1 first, prime, principal, chief, main, leading, pre-eminent, cardinal, fundamental, basic, essential, predominant, elementary, elemental, underlying:
The primary reason I want to see you is to discuss your future with the company. The primary meaning of a word is given first.
2 earliest, first, original, initial, primitive, primeval, primordial, embryonic, germinal, beginning, ultimate:
The primary source of life was possibly a sort of soup containing proteins and other molecules
3 firsthand, direct, immediate:
Bauxite is the primary source of aluminium ore.
4 elementary, basic, rudimentary, fundamental:
One of the primary lessons we are taught is consideration for others
5 unmixed, unadulterated, pure, simple, rudimentary, fundamental, principal:
The primary colours in art are red, yellow, and blue.