1) Complemental 2) Complementary 3) Completing 4) Dispensable 5) Expendable 6) Extrinsic 7) Incidental 8) Insubstantial 9) Nonessential 10) Not absolutely necessary 11) Not basic or fundamental 12) Not essential 13) Not necessary 14) Not required 15) Secondary 16) Unessential 17) Unimportant 18) Unnecessary 
• (a.) Not essential; unessential. • (a.) Having no essence or being.
In`es·sen'tial adjective [ Prefix in- not + essential : confer French inessentiel .] 1. Having no essence or being. H. Brooke. « The womb of inessential Naught.» Shelley. 2. Not essential; unessential. 
[adj] - not absolutely necessary 2. [adj] - not basic or fundamental 3. [n] - anything that is not essential
unessential adjective not basic or fundamental
not essential; not necessary; nonessential. · without essence; insubstantial.