confirm the truth of

read for errors

verify by using a duplicate register for comparison

check once more to be absolutely sure

check out conflicting sources; crosscheck facts, for example

make sure of

put a check mark on or near or next to

verify by consulting a source or authority

find out, learn, or determine with certainty, usually by making an inquiry or other effort

check or regulate (a scientific experiment) by conducting a parallel experiment or comparing with another standard