vital

adj

1.
urgently needed; absolutely necessary
critical
Derived from:
vitalness
2.
performing an essential function in the living body
life-sustaining
Derived from:
vitality vitalness
3.
full of spirit; full of life
lively
Derived from:
vitality vitalize
4.
manifesting or characteristic of life
Derived from:
vitality vitalize vitalness