vital

adjective

• Relating to, or characteristic of life.

  "vital energies; vital functions; vital actions"

• Necessary to the continuation of life; being the seat of life; being that on which life depends.

  "The brain is a vital organ."

• Invigorating or life-giving.
• Necessary to continued existence.

  "The transition to farming was vital for the creation of civilisation."

• Relating to the recording of life events.

  "Birth, marriage and death certificates are vital records."

• Very important.

  "It is vital that you don't forget to do your homework."

• Containing life; living.
• Capable of living; in a state to live; viable.