base/basis (n.) – the most important part of something, from which other things can develop. ---- base (v.), based (adj)
Algebra forms the basis of more complex subjects such as calculus.
proof (n.) – a fact or a piece of information that shows something exists or is true. ---- prove (v.), proven (adj.)
Fingerprints at the scene of the crime prove that Mr. Anderson was there.
research (n.) – detailed study of a subject in order to discover new information. ---- research (v.), researcher (n.)
Psychologists do a lot of research to better understand the human brain.