adjective

1. of, concerned with, or manifesting life vital energy
2. 1. necessary or essential to life; being a source or support of life vital organs
   2. affecting, esp. destroying, life; critical, esp. fatal a vital wound
3. 1. essential to the existence or continuance of something; indispensable a vital function
   2. of crucial importance a vital matter
4. affecting the validity, truth, etc. of something a vital error
5. full of life and vigor; energetic a vital personality

Etymology: ME < MFr < L vitalis, vital < vita, life, akin to vivere, to live: see bio-

noun

1. the vital organs, as the heart, brain, lungs, etc.
2. the essential parts of anything, indispensable for its existence, continuance, etc.