Synonyms for Ascertain (same or very similar meaning)
WordNet sense 1 (find out, learn, or determine with certainty, usually by making an inquiry or other effort):
check, determine, learn, see, watch, find outWordNet sense 2 (establish after a calculation, investigation, experiment, survey, or study):
findWordNet sense 3 (be careful or certain to do something; make certain of something):
assure, control, ensure, insure, see to itFrom the ODE community, based on WordNetadd/edit