1. [adj]  manifesting or characteristic of life; "a vital, living organism"; "vital signs"
2. [adj]  full of spirit; "a dynamic full of life woman"; "a vital and charismatic leader"; "this whole lively world"
3. [adj]  performing an essential function in the living body; "vital organs"; "blood and other vital fluids"; "the loss of vital heat in shock"; "a vital spot"; "life-giving love and praise"
4. [adj]  urgently needed; absolutely necessary; "a critical element of the plan"; "critical medical supplies"; "vital for a healthy society"; "of vital interest"

1. \Vi"tal\, a. [F., fr. L. vitalis, fr. vita life; akin to
   vivere to live. See {Vivid}.]
   1. Belonging or relating to life, either animal or vegetable;
      as, vital energies; vital functions; vital actions.
   2. Contributing to life; necessary to, or supporting, life;
      as, vital blood.
            Do the heavens afford him vital food? --Spenser.
            And vital virtue infused, and vital warmth.
                                                  --Milton.
   3. Containing life; living. ``Spirits that live throughout,
      vital in every part.'' --Milton.
   4. Being the seat of life; being that on which life depends;
      mortal.
            The dart flew on, and pierced a vital part. --Pope.
   5. Very necessary; highly important; essential.
            A competence is vital to content.     --Young.
   6. Capable of living; in a state to live; viable. [R.]
            Pythagoras and Hippocrates . . . affirm the birth of
            the seventh month to be vital.        --Sir T.
                                                  Browne.
   {Vital air}, oxygen gas; -- so called because essential to
      animal life. [Obs.]
   {Vital capacity} (Physiol.), the breathing capacity of the
      lungs; -- expressed by the number of cubic inches of air
      which can be forcibly exhaled after a full inspiration.
   {Vital force}. (Biol.) See under {Force}. The vital forces,
      according to Cope, are nerve force (neurism), growth force
      (bathmism), and thought force (phrenism), all under the
      direction and control of the vital principle. Apart from
      the phenomena of consciousness, vital actions no longer
      need to be considered as of a mysterious and unfathomable
      character, nor vital force as anything other than a form
      of physical energy derived from, and convertible into,
      other well-known forces of nature.
   {Vital functions} (Physiol.), those functions or actions of
      the body on which life is directly dependent, as the
      circulation of the blood, digestion, etc.
   {Vital principle}, an immaterial force, to which the
      functions peculiar to living beings are ascribed.
   {Vital statistics}, statistics respecting the duration of
      life, and the circumstances affecting its duration.
   {Vital tripod}. (Physiol.) See under {Tripod}.
   {Vital vessels} (Bot.), a name for latex tubes, now disused.
      See {Latex}.
   

2. \Vi"tal\, n.
   A vital part; one of the vitals. [R.]
   

A semantics language using FSL, developed by Mondshein in 1967.

[Sammet 1969, p. 641].