vital
adjective(vi-tal)
urgently needed; absolutely necessary
Examples:
Vital for a healthy society. 
Of vital interest. 
vital
adjective(vi-tal)
performing an essential function in the living body
Synonyms: life-sustaining, 
Examples:
Vital organs. 
Blood and other vital fluids. 
The loss of vital heat in shock. 
A vital spot. 
vital
adjective(vi-tal)
full of spirit; full of life
Examples:
A vital and charismatic leader. 
vital
adjective(vi-tal)
manifesting or characteristic of life
Examples:
A vital, living organism. 
Vital signs.