as·cer·tain 
(ăs′ər-tān)
(ăs′ər-tān)tr.v. as·cer·tained, as·cer·tain·ing, as·cer·tains
1. To discover with certainty, as through examination or experimentation. See Synonyms at discover.
2. Archaic To make certain, definite, and precise.
[Middle English acertainen, to inform, from Old French acertener, ascertain- : a-, to (from Latin ad-; see AD-) + certain, certain; see CERTAIN.]
as′cer·taina·ble adj.
as′cer·taina·ble·ness n.
as′cer·taina·bly adv.
as′cer·tainment n.