1. (adjective) serving as an essential component

• cardinal
• central
• fundamental
• key

2. (adjective) having existed from the beginning; in an earliest or original stage or state

• aboriginal
• primaeval
• primeval
• primordial

1. (adjective) serving as an essential component

• important
• of import

2. (adjective) having existed from the beginning; in an earliest or original stage or state

• early

1. (adjective) serving as an essential component

• center
• center of attention
• centre
• centre of attention
• center
• centre
• core
• essence
• gist
• heart
• heart and soul
• inwardness
• kernel
• marrow
• meat
• nitty-gritty
• nub
• pith
• substance
• sum