Merriam-Webster Collegiate Dictionary - vital

 adjective  Etymology: Middle English, from Latin ~is of life, from vita life; akin to Latin vivere to live — more at quick  Date: 14th century  1.  a. existing as a manifestation of life  b. concerned with or necessary to the maintenance of life ~ organs blood and other ~ fluids  2. full of life and vigor ; animated  3. characteristic of life or living beings  4.  a. fundamentally concerned with or affecting life or living beings: as  (1) tending to renew or refresh the living ; invigorating  (2) destructive to life ; mortal  b. of the utmost importance a ~ clue ~ resources  5. recording data relating to lives  6. of, relating to, or constituting the staining of living tissues  Synonyms: see essential  • ~ly adverb