Synonyms and related words :
ambition, aspiration, basis, calling, cause, consideration, font, fount, fountain, fountainhead, goal, ground, guiding light, guiding star, headspring, headstream, headwater, ideal, inspiration, intention, lodestar, matter, mine, motive, principle, quarry, reason, riverhead, sake, score, source, spring, springhead, ulterior motive, vocation, well, wellhead, wellspring