"ascertain" in the verb sense
1. determine, find, find out, ascertain
establish after a calculation, investigation, experiment, survey, or study
"find the product of two numbers"
"The physicist who found the elusive particle won the Nobel Prize"
2. see, check, insure, see to it, ensure, control, ascertain, assure
be careful or certain to do something make certain of something
"He verified that the valves were closed"
"See that the curtains are closed"
"control the quality of the product"
3. determine, check, find out, see, ascertain, watch, learn
find out, learn, or determine with certainty, usually by making an inquiry or other effort
"I want to see whether she speaks French"
"See whether it works"
"find out if he speaks Russian"
"Check whether the train leaves on time"
learn or discover with certainty
Source: WordNet® (An amazing lexical database of English)
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