What does annotation mean?
An annotation is a note or comment added to a text, image, diagram, or other document in order to explain, interpret, critique, or supplement its content. The word also denotes the act of adding such notes — a practice as old as writing itself, from medieval scribes glossing manuscripts to modern students marking up textbooks. Annotations range from brief marginal remarks to extensive scholarly commentary, and the term appears across many fields: an annotated bibliography lists sources with evaluative notes, while in computing, annotation refers to metadata attached to data, code, or images, such as the labels used to train machine-learning models. Derived from the Latin annotare, meaning 'to note down,' the word carries a neutral to scholarly connotation and signals careful, engaged reading or analysis. Whether in a printed margin, a PDF comment, or a dataset label, an annotation adds a second layer of meaning atop the original material.
A note or comment added to a text, image, diagram, or other document to explain, criticize, or supplement its content.
"Each page of the annotated edition carries footnotes and annotations clarifying the archaic language."
In academic publishing, 'annotation' often specifically means a concise descriptive or evaluative note, as in an annotated bibliography.
The act or process of adding such notes; commentary on a work.
"Careful annotation of the dataset took the research team nearly six months."
The plural is standard when referring to more than one note; the singular is used for the practice or act as a whole (often phrased as 'the annotation of a text').
"The manuscript's annotations were added by at least three different hands over two centuries."
Medieval monks filled book margins with annotations so dense that scholars today still mine them for lost knowledge — your scribbled notes might outlive you.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of annotation
Annotation derives from the Latin verb annotare, meaning 'to mark' or 'to note down,' formed from ad- ('to, toward') plus notare ('to mark'), itself rooted in nota, 'a mark or sign.' The word entered English in the late sixteenth or early seventeenth century, initially describing scholarly notes appended to classical texts. It shares its Latin root with annotate, notation, denotation, and connotation, all of which involve marking or signifying.
Related word forms
How annotation is actually used
Annotation is a formal-to-neutral word common in academic, legal, and technical contexts. In computing it has become especially prominent through machine learning (data labeling) and programming languages (e.g., Java annotations). The plural 'annotations' is standard when referring to multiple notes.
Easily confused with annotation
Notarization is the official certification of a document by a notary public, whereas annotation is simply the addition of explanatory notes.