basisEnglishOxford American Thesaurusbasis noun 1 the factual basis for his criticism: foundation, support, base, footing; reasoning, rationale, defense; reason, grounds, justification, rationalization, motive, motivation, cause. 2 the White Paper formed the basis of the Consumer Credit Act: starting point, base, point of departure, beginning, premise; fundamental point/principle, principal constituent, main ingredient, cornerstone, core, heart, thrust, essence, kernel, nub, underpinning, groundwork. 3 those who are studying on a part-time basis: footing, condition, status, position; arrangement, system, method, procedure, way.