DictionaryAI

datum

DAY-tuhm/ˈdeɪtəm/

4 meanings of datum

Practice

  1. 1
    noun
    Singular of data.

    Each datum was recorded by hand in the laboratory notebook.

    A single datum on its own rarely tells the whole story.

    UsageIn everyday writing, one item is more often called a data point or a piece of data.

    Note

    Here the Latin singular stands behind the everyday plural data, and it survives mainly in scientific, technical and philosophical writing. A datum belongs to a data set the way one reading belongs to a table: a single value among many.

  2. 2
    reference levelnouncountable
    A fixed point, line, or surface used as a reference from which positions or elevations are measured.

    Surveyors established a permanent datum before mapping the valley's elevations.

    All heights on the chart are measured from a single tidal datum.

    UsageThe plural in surveying is usually datums: chart datums, tidal datums.

    Similarbenchmark, baseline

    Note

    In leveling, a permanent benchmark can serve as the datum. A tidal datum is the water level from which predicted tide heights are counted.

    Checked 2 Nov 2026 · 2 facts

Less common meanings

  1. 3
    noun
    In search and rescue, the estimated position of a person or object in the water, worked out from the last known position corrected for drift.
  2. 4
    verb
    To adjust measurements, especially seismic data, so that they appear to have been recorded at a chosen reference level or surface.

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Origin

English took the word directly from Latin datum, meaning "a given." Die is a doublet.