vi·tal 
(vītl)
(vītl)adj.
1.
a. Of, relating to, or characteristic of life: vital strength. See Synonyms at living.
b. Necessary to the continuation of life; life-sustaining: a vital organ; vital nutrients.
c. Used or done on a living cell or tissue: vital dyes; vital staining.
d. Concerned with or recording data pertinent to lives: vital records.
2. Full of life or energy; animated: "The population of the teeming, vital slum ... declined" (Rick Hampson).
3.
a. Necessary to continued existence or effectiveness: "Irrigation was vital to early civilization" (William H. McNeill).
b. Extremely important; essential: "A vital component of any democracy is a free labor movement" (Bayard Rustin).
4. Destructive to life; fatal: a vital injury.
[Middle English, from Old French, from Latin vītālis, from vīta, life; see gwei- in the Appendix of Indo-European roots.]
vital·ly adv.
vital·ness n.