# annotation

/ˌænəˈteɪʃən/ (US) · /ˌænəʊtˈeɪʃən/ (UK)

Source: https://englishreference.com/word/annotation
Updated: 2026-08-27

## Senses

### 1. a written note

noun · CEFR B2 · Academic

a short note added to a book or document to explain a difficult part or add an opinion.

For teachers: a critical or explanatory commentary added to a text. Countable in the sense of a single note; uncountable when referring to the practice.

- The student's copy of the play was full of helpful annotations in the margins.
- The scholar provided a detailed annotation for each archaic term, ensuring the medieval manuscript remained accessible to modern researchers.

### 2. computing/data

noun · CEFR C1 · Technical

extra information or labels added to data or computer code to help a machine or person understand it.

For teachers: metadata or labels added to a document, program, or dataset to provide context or facilitate machine learning.

- The programmer added an annotation to the code to explain why the function was necessary.
- Accurate image annotation is a critical step in training the neural network to recognize different types of vehicles in urban environments.

### 3. the act of adding notes

noun · CEFR B2 · Academic

the process of adding notes or labels to something.

For teachers: the act or process of furnishing a text or dataset with explanatory notes or metadata.

- Annotation takes a long time but it makes the research much easier to follow.
- The systematic annotation of the genome required years of collaborative effort from laboratories across the globe.

## Examples

- I added a small annotation to the margin of the book.
- The developer included a detailed annotation in the source code to explain why the specific algorithm was chosen.
- Scholarly editions of classic literature often feature extensive annotations that clarify archaic references and provide historical context for the modern reader.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.