English Reference
noun

annotation

n.
US /ˌænəˈteɪʃən/ UK /ˌænəʊtˈeɪʃən/ an·no·ta·tion UK spelling annotations

  1. 01 B2 Upper Intermediate Academic

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

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

    Simple

    The student's copy of the play was full of helpful annotations in the margins.

    In context

    The scholar provided a detailed annotation for each archaic term, ensuring the medieval manuscript remained accessible to modern researchers.

  2. 02 C1 Advanced Technical Computing

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

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

    Simple

    The programmer added an annotation to the code to explain why the function was necessary.

    In context

    Accurate image annotation is a critical step in training the neural network to recognize different types of vehicles in urban environments.

  3. 03 B2 Upper Intermediate Academic

    the process of adding notes or labels to something.

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

    Simple

    Annotation takes a long time but it makes the research much easier to follow.

    In context

    The systematic annotation of the genome required years of collaborative effort from laboratories across the globe.

    labelingcommentating

In the fast-growing field of data annotation, workers in a small city in south India train A.I.

The New York Times· 20 Aug 2026

Each page features around 25 lines of Homeric text surrounded by extensive annotations.

Smithsonian Magazine· 17 Jul 2026

From Latin annotātiōnem, accusative singular of annotātiō (“remark, annotation”), from annotātus, perfect passive participle of annotō (“note down, remark”). Equivalent to annotate + -ion.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level B2 · Upper Intermediate
Frequency Occasional
Updated