da·tum 
(dātəm, dătəm, dätəm)
(dātəm, dătəm, dätəm)n.
1. pl. da·ta (-tə) A fact or proposition used to draw a conclusion or make a decision. See Usage Note at data.
2. pl. da·tums A point, line, or surface used as a reference, as in surveying, mapping, or geology.
[Latin, something given, from neuter past participle of dare, to give; see dō- in the Appendix of Indo-European roots.]