noun (n)

• the fundamental assumptions from which something is begun or developed or calculated or explained(noun.cognition)

  Synonym:
  base, basis, cornerstone, foundation, groundwork
  

  source: wordnet30
• the fleshy part of the human body that you sit on(noun.body)

  Synonym:
  arse, ass, backside, behind, bottom, bum, buns, butt, buttocks, can, derriere, fanny, hind end, hindquarters, keister, nates, posterior, prat, rear, rear end, rump
  

  source: wordnet30
• lowest support of a structure(noun.artifact)

  Synonym:
  base, foot, foundation, groundwork, substructure, understructure
  

  source: wordnet30
• Foundation.(noun)

  source: webster1913