Information, a fact, a figure, etc. used to make a decision or to come to a result: Data are known or assumed; such as, facts or figures from which a conclusion, or conclusions, can be determined.

Although rarely used properly, if at all, datum should be expressed in the singular sense, for example: "There is one datum on this page that is not correct."

Using the word "fact" instead of datum probably would make one's writing easier to understand and decrease anxiety about the proper use of datum.

Data, as the plural of datum, requires a plural verb in Latin and in English."

People often read; especially, in technical, scientific, and business writings; such usages as, "The data is inconclusive." It should be: "These or Those data are inconclusive."

One piece of material collected and recorded as significant evidence by an archaeologist (the plural is used as a singular): Archaeological data falls into four classes: artifacts, ecofacts, features, and structures.

A global datum reference for expressing the exact position of places on Earth: The geodetic datum consists of five quantities: the latitude and longitude of an initial point, the azimuth of a line from this point, and two constants necessary to define the terrestrial spheroid.

Horizontal datum is used for describing a point on the Earth's surface, in latitude and longitude or another coordinate system. Vertical datum measures elevations or depths.