1. (

• cardinal ,
• central ,
• fundamental ,
• key ,
• primal

) serving as an essential component; "a cardinal rule"; "the central cause of the problem"; "an example that was fundamental to the argument"; "computers are fundamental to modern industrial structure" ;

2. (

• aboriginal ,
• primal ,
• primeval ,
• primaeval ,
• primordial

) having existed from the beginning; in an earliest or original stage or state; "aboriginal forests"; "primal eras before the appearance of life on earth"; "the forest primeval"; "primordial matter"; "primordial forms of life" ;