# Commenting and Annotating Lab Notebook Entries By the end of this article you will be able to write a complete [lab notebook](/knowledge/molecular-biology/lab-notebook) entry, add comments and annotations that a stranger can understand a year later, give useful feedback on a labmate's entry, and choose between a paper notebook and an electronic lab notebook for your situation. You need nothing more than your current notebook (paper or electronic), a pen or a text cursor, and about twenty minutes to practice the walkthrough below. Commenting and annotating lab notebook entries is the difference between a notebook that documents what happened and a notebook that explains why it happened. The entry records the observation. The comment and the annotation explain the decision behind it, flag the anomaly, and tell the next reader what to trust and what to repeat. ## Why Comments and Annotations Matter A lab notebook entry has a recognized structure. A widely used guided-inquiry activity for teaching notebook skills asks students to write entries that include a title, date, author, purpose, methods, results, and conclusions, and then to describe how those entries support the research project [1]. That structure covers the record itself. Comments and annotations sit on top of the record. They are the interpretive layer. This interpretive layer matters for three reasons: 1. **Future you.** Six months from now you will not remember why you changed the incubation time. A dated comment saying "increased to 45 min because band intensity was weak on 09/14" saves you a repeat experiment. 2. **Other people.** Instructors, reviewers, patent attorneys, and collaborators read notebooks. An entry with no annotation forces every reader to reconstruct your reasoning from raw data. 3. **Machines, increasingly.** Archival lab notebooks are now being digitized and segmented so that entry types can be extracted automatically and reused for scientific study. Researchers testing these methods found that notebooks contain valuable data about research conditions, steps, and outcomes, but only well-structured entries can be parsed reliably. A notebook full of unstructured marginalia resists that kind of reuse, while one with clearly labeled entries feeds directly into it. ## Comments, Annotations, and Entries: Definitions Keep three terms separate in your head because instructors and ELN documentation use them differently. **Entry.** The dated record of one experiment or activity. It contains the header, purpose, methods, results, and conclusions [1]. **Annotation.** A note attached to a specific piece of data inside the entry. In a paper notebook this is an arrow, bracket, or margin note tied to a particular gel lane, table row, or graph point. In an electronic lab notebook it is often a tagged note anchored to an uploaded file or a highlighted region of an image. **Comment.** A dated, signed remark that adds interpretation, context, or correction. A comment can attach to the whole entry or to a specific item, and it typically answers the question "what did I conclude or decide at this moment?" The distinction matters in electronic systems because these two elements behave differently. Most ELN platforms treat annotations as anchored notes and comments as timestamped, attributable messages in a thread. That timestamped thread is one of the core capabilities researchers ask for in an electronic notebook. The eCAT ELN, developed with input from academic and government labs, was built around exactly these features: a permissions system, controlled sharing, an audit trail, electronic signature, and search, wrapped in an interface that resembles a paper notebook [2]. ## How to Comment on Lab Notebook Entries Step by Step ![Six steps for commenting on a lab notebook entry, from confirming the entry is complete to adding a cross-reference.](/article-images/illustrations/how-to-comment-on-lab-notebook-entries-comment-steps.webp) This walkthrough covers both paper and electronic notebooks. Work through it once with a real entry from your last experiment. ### Step 1: Start from a complete entry You cannot annotate a hollow record. Before adding any comment, confirm the entry contains the required parts: title, date, author, purpose, methods, results, and conclusions [1]. If any part is missing, write it in before you annotate. Annotating an incomplete entry is like adding footnotes to a blank page. A reusable skeleton looks like this: ```markdown # Entry 042: PCR optimization of 16S rRNA amplicon Date: 2026-11-10 Author: Z. Khalid Purpose: Determine annealing temperature that yields a single clean band for isolate B7. Methods: [Gradient PCR](/knowledge/molecular-biology/gradient-pcr), 55.0 to 65.0 C, 12 cycles. Reagents and lot numbers listed on reagent page R-18. Results: Gel image attached (IMG_042.png). Single band at ~1500 bp at 60.0 and 61.5 C. Conclusions: Carry forward 60.0 C for isolate B7 amplification. ``` Expected output when you open this entry later: you can answer what was done, why, and what was decided without asking anyone. ### Step 2: Add annotations at the data level Now anchor notes to the specific data points that carry meaning. On paper, draw a clean line from the margin to the gel lane or table row. In an ELN, use the annotation or highlight tool on the attached file. Write the annotation in the same tense as the entry, keep it under about twenty words, and state an observation rather than a feeling. ```text Annotation examples (data-level): IMG_042.png, lane 4: "Single band, expected size. No primer dimers visible." Table 1, row 60.0 C: "Duplicate reactions agree within 0.2 Ct." Graph, 30 min timepoint: "Outlier, pipetting error suspected. See comment below." ``` Expected output: a reader can hover or look at the margin and know immediately which observation each note describes. ### Step 3: Write comments that record decisions A comment records a decision and its justification at a moment in time. Use a consistent, short pattern: date, initials, observation, decision, reason. On paper this goes directly beneath the relevant section. In an ELN it goes in the entry's comment field or thread. ```text Comment (entry level): 2026-11-10, ZK. Band at 58.5 C was faint, so the gradient lower bound is too permissive for this primer pair. Decision: run confirmatory PCR at 60.0 C only, duplicates. Reason: 60.0 and 61.5 C both gave single bands, 60.0 C is closer to published conditions for this primer set. ``` Notice what this comment does that the entry alone does not. It explains why the confirmatory run exists, which prevents a future reader from thinking the experiment was duplicated out of sloppiness. ### Step 4: Flag errors without erasing In a paper notebook, never erase or remove an error. Draw a single line through it, write the correction nearby, and initial and date the change. Then add a comment explaining what went wrong. This preserves the audit trail, the same principle that underlies the electronic signature and audit trail features built into commercial and academic ELNs [2]. ```text Error handling (paper): "5 mL buffer" (single strike-through) Corrected: 15 mL buffer. ZK 2026-11-10 Comment: "[Transcription error](/knowledge/molecular-biology/transcription-error) from recipe card R-3. Volume actually dispensed was 15 mL, verified on balance." ``` In an ELN, most platforms keep revision history automatically, so you edit forward and the audit trail shows what changed and when [2]. ### Step 5: Sign and date every comment An unsigned comment has no provenance. Every annotation and comment carries your initials and the date, even in a solo notebook. In electronic systems this is usually automatic, which is one reason student users in a bioprocess engineering course reported that the ELN was better than paper for compliance with good documentation practices [3]. ### Step 6: Close the entry with a cross-reference If a later experiment corrects or extends this one, return and add a forward-looking comment. This is the notebook equivalent of a hyperlink. ```text Follow-up comment: 2026-11-13, ZK. Confirmatory PCR succeeded at 60.0 C. See Entry 044. Conclusion in this entry stands. ``` Expected output: anyone reading entry 042 knows the story continued and where to find the ending. ## A Lab Notebook Template You Can Reuse A good lab notebook template bakes annotation slots in so commenting becomes automatic rather than an afterthought. The template below combines the required entry elements from the guided-inquiry notebook curriculum [1] with explicit fields for annotations and follow-up. ```markdown # Entry #[number]: [Short descriptive title] Date: [YYYY-MM-DD] Author: [Name, initials] Purpose: [1-2 sentences, what question this entry answers] Methods: [Protocol name/version] [Deviations from protocol, each with initials + date] [Reagent lot numbers or reference to reagent log] Results: [Raw data, files, images attached or pasted] Data annotations: - [file/location]: [observation, initials, date] - [file/location]: [observation, initials, date] Conclusions: [What the results mean, 1-3 sentences] Comments / Decisions: [Date, initials]: [decision] because [reason] Flags: [ ] Error occurred (describe, strike-through + initials on paper) [ ] Needs repeat [ ] Cross-reference: [Entry #] ``` In teaching labs, instructors report that templates and structured feedback are easier to deliver when students use an electronic notebook rather than paper, because entries and assignments can be graded in a timely and collaborative way [4]. ## How to Comment on Someone Else's Entry Peer and instructor comments follow different rules than your own annotations. Your own comments record decisions. Comments on other people's entries should be actionable, specific, and tied to a checkable standard. The strongest evidence on what makes lab-based comments useful comes from competency-based assessment studies. In a gross anatomy course for first-year medical students, structured self- and peer-assessments of communication skills showed significant improvement over the course, with peer-assessment scores rising from a mean of 4.70 to 4.87 on a scale where those values apply, and self-assessment scores rising from 4.50 to 4.77 [5]. Thematic analysis of student reflection entries showed that students developed skills in imparting information and gathering information, which are exactly the two functions of a good notebook comment [5]. A companion study on professionalism found that peer-assessment scores improved significantly over the course while self-assessments did not change significantly [6]. The practical lesson: other people's evaluations of your record keeping catch things your self-evaluation misses, so treat peer comments on your notebook as data, not criticism. ### Tips for useful peer comments - **Name the specific element.** "The conclusion in Entry 042 does not follow from Table 1" beats "this is unclear." - **Anchor to data.** Point at the lane, row, or figure that triggered the comment. - **Offer the check.** "Recompute the dilution factor, I get 1:100 not 1:10" gives the author something to verify. - **Separate observation from opinion.** State what you see first, then what you would change. - **Sign it.** Anonymous comments remove accountability and make follow-up impossible. ### Common phrasings that work ```text Weak comment: "Looks good." Strong comment: "Methods section lists the buffer but not the lot number. Lot numbers appear elsewhere in the notebook (R-18), so add the reference here." Weak comment: "Weird result." Strong comment: "Lane 6 shows two bands where the conclusion claims one. Either the image is wrong or the conclusion overstates the result. Check IMG_042.png." ``` ## Electronic Lab Notebook Comparison ![Comparison table of paper notebooks, generic cloud ELNs and open-source course notebooks across timestamps, audit trails, search and remote access.](/article-images/illustrations/how-to-comment-on-lab-notebook-entries-paper-vs-eln.webp) Choosing where to comment and annotate depends on the platform. The table below compares the annotation-relevant capabilities of paper notebooks and the electronic approaches documented in the literature. | Capability | Paper notebook | Generic cloud ELN | Open-source course e-LN | |--|--|--|--| | Timestamped comments | Manual, must hand-write | Automatic | Automatic | | Audit trail of edits | Strike-through only | Built in [2] | Revision history [4] | | Search across entries | None (unless indexed) | Full text search [2] | Web search [4] | | Anchored image annotations | Margin arrows | Highlight tools | Pasted digital data with notes [4] | | Handling large digital datasets | Poor, prints or references | Strong [3] | Strong, designed for digital data [4] | | Real-time remote monitoring | Impossible | Enabled [3] | Possible with browser access [4] | | Cross-platform data exchange | N/A | Platform dependent | API bridges emerging [7] | | Cost | Notebook only | Varies by vendor | Free, open source [4] | Several patterns from the literature deserve emphasis. A cloud-based ELN implemented in a bioprocess engineering teaching lab improved workflow, quick data recording and archiving, data sharing, and collaboration, and enabled real-time and remote monitoring of experiments [3]. An open-source electronic notebook built for an undergraduate genomics course solved the core paper limitation, that digital data such as gel images, spectrophotometer readings, and bioinformatics output are difficult to collect in a paper notebook, and students reported that templates and feedback were easier in the electronic format [4]. Free options exist even where budgets are tight, as demonstrated by a no-cost ELN implementation in an introductory engineering design course [8]. One caution when comparing platforms. ELN platforms do not interoperate natively, and researchers have built tools such as ELNdataBridge specifically because exchanging data between different ELN systems required a Python-API-based adapter to map values and entry types between platforms [7]. If your lab or collaborator uses a different ELN, check export formats before you commit years of annotated entries to one vendor. Comments written in a proprietary format may not travel. A different kind of "notebook" also deserves mention because students encounter it. Jupyter notebooks used in physical chemistry labs mix instructions, interactive code, and results in one document, and the annotation habit transfers directly: markdown cells in a Jupyter notebook function as comments and annotations between code cells, and students who learned this pattern carried the skill into other courses [9]. ## How to Comment on Lab Notebook Entries: Tips These tips compress the practices above into habits you can apply during the experiment, not after. 1. **Comment in the moment.** A comment written at the bench records what you believed at the time. A comment written a week later records what you now wish you had believed. 2. **Use the five-part comment.** Date, initials, observation, decision, reason. If any part is missing, the comment loses its value as evidence. 3. **Annotate failures louder than successes.** The failed reaction with a clear annotation of suspected cause is the single most valuable thing in a notebook. 4. **Keep one idea per annotation.** Two observations crammed into one margin note become unfindable later. 5. **Write for a stranger.** The guided-inquiry notebook curriculum explicitly targets scientific communication as a learning objective, because notebook writing is communication training [1]. 6. **Cross-reference everything.** Entry numbers are cheap. "See Entry 044" costs three words and saves an hour. 7. **Review weekly.** Read your own comments from the past week. Anything you cannot understand is a warning about entries still to come. 8. **Match the platform's strengths.** On paper, invest in margins wide enough to annotate. In an ELN, learn the highlight and comment tools in week one rather than improvising [3]. ## Common Mistakes and Limitations These are the errors that show up repeatedly when students and new researchers comment on lab notebook entries. **Erasing or deleting.** Removing an error destroys provenance. Strike through on paper, edit forward in an ELN, and comment on what changed [2]. **Unsigned or undated comments.** An annotation without initials and a date cannot be attributed when questions arise later. This is the most common single defect in reviewed notebooks. **Vague praise.** "Good" and "nice" contain no information. A comment earns its place by naming what is right or wrong and why. **Annotating conclusions instead of data.** "The experiment worked" is a conclusion, not an annotation. Anchor notes to the specific lane, row, or value that justifies the conclusion. **Writing comments after the fact without marking them.** A comment added later must say so. "Added 2026-11-15, ZK, after reviewing raw instrument file" is honest and preserves the timeline. Backdating or presenting a late comment as contemporaneous undermines the whole record. **Over-annotating.** Forty margin notes on one gel is noise. Annotate the observations a reader needs to reconstruct your reasoning, not every glimpse of the data. **Ignoring the entry structure.** Comments cannot rescue an entry that lacks purpose, methods, results, and conclusions. Fix the structure first. **Assuming comments are private.** Notebooks in an ELN are shared and searchable by design [2]. Write every comment as though your supervisor, your collaborator, and a reviewer will read it, because eventually they may. **Platform lock-in.** Years of annotated entries in one ELN may be hard to move. The need for API-based bridges between platforms to transfer values and entry types shows that portability is not automatic [7]. Export annotated data periodically. **One limitation of the evidence base.** The strongest quantitative studies of notebook commenting come from structured teaching environments, particularly medical anatomy labs and engineering and genomics courses, where comment quality was assessed with defined instruments [5][3][6]. Individual labs vary in their conventions, so ask your supervisor or instructor which local rules apply before standardizing your format. ## Next Steps Adopt the template in this article for your next entry. After five entries, reread all five and mark every comment that fails the five-part test. If you lead a course or a small lab, the guided-inquiry notebook activity has been used across hundreds of students in multiple lab sections and is designed to be modified, which makes it a practical starting point for teaching these habits at scale [1]. If you are choosing a platform, run the electronic lab notebook comparison table against two or three candidates and test the comment and annotation tools on a real file before committing [3][2][4]. ## Frequently Asked Questions ### What is the difference between a comment and an annotation in a lab notebook? An annotation attaches a note to a specific piece of data, such as one gel lane or one table row. A comment is a dated, signed remark that records a decision, interpretation, or correction for the entry as a whole or for one item in it. Both belong in a complete notebook. ### How do I comment on lab notebook entries step by step? First confirm the entry has title, date, author, purpose, methods, results, and conclusions. Then annotate the specific data points, write entry-level comments that state observation, decision, and reason, strike through errors without erasing, sign and date every remark, and close with cross-references to related entries. ### Should notebook comments be handwritten or typed? Either, as long as they are signed and dated. Electronic notebooks automate timestamps, searching, and audit trails, and students have rated them better than paper for compliance, while paper remains fully acceptable when the discipline of signing and dating is maintained. ### What should I write when an experiment fails? Write the most valuable comment in the notebook. State what was expected, what was observed, your leading hypothesis for the failure, and what you will change next. Flag the entry for follow-up and cross-reference the repeat experiment once it exists. ### How do instructors evaluate notebook comments? Many rubrics assess whether entries contain the required structural elements and whether the writing demonstrates clear scientific communication. In competency-based courses, structured peer and self-assessments have shown measurable improvement in communication skills over a course, and reflection entries showed students developing the ability to impart and gather information. ### Can I add comments to a notebook entry after the fact? Yes, as long as the comment states its own date. A late comment that honestly says "added 2026-11-15 after reviewing the instrument file" preserves the record. Presenting a late comment as if it were written at the bench does not. ### How do electronic lab notebooks handle commenting differently from paper? ELNs timestamp every comment automatically, maintain a full audit trail of edits, support full-text search, and let multiple people comment on the same entry in real time from remote locations. Paper requires hand-written dates and strike-throughs and cannot be searched or monitored remotely. ### What makes a good peer comment on a labmate's entry? Name the specific element you are commenting on, anchor the comment to a checkable piece of data, state what you observe before what you recommend, and sign your name. "Lane 6 shows two bands but the conclusion claims one, check IMG_042.png" is a useful peer comment. "Looks good" is not. ## Sources 1. [Lab Notebook POGIL (process-oriented guided-inquiry learning) activity](https://doi.org/10.37590/able.v46.abs23) 2. [eCAT: Online electronic lab notebook for scientific research.](https://pubmed.ncbi.nlm.nih.gov/20334629/) 3. [Implementation and use of cloud-based electronic lab notebook in a bioprocess engineering teaching laboratory.](https://pubmed.ncbi.nlm.nih.gov/29201138/) 4. [An Open Source, Collaborative Electronic Notebook for Undergraduate Laboratory Classes](https://doi.org/10.24918/CS.2015.1) 5. [Incorporating competency-based medical education in the gross anatomy lab context. A mixed-methods study of first-year medical students' communication competency development over the gross anatomy course](https://pubmed.ncbi.nlm.nih.gov/40481710/) 6. [A Mixed-Methods Investigation of First-Year Medical Students’ Professionalism Competency Development over the Gross Anatomy Course](https://pubmed.ncbi.nlm.nih.gov/40144103/) 7. [ELNdataBridge: facilitating data exchange and collaboration by linking Electronic Lab Notebooks via API](https://pubmed.ncbi.nlm.nih.gov/40420243/) 8. [No-cost Implementation of Electronic Lab Notebooks in an Intro Engineering Design Course](https://doi.org/10.18260/1-2--30841) 9. [Integrating Python into a Physical Chemistry Lab](https://doi.org/10.1021/acs.jchemed.2c00193)