Some synonyms for Vital are-
Necessary, important
luminosity is synonymous to brightness
Decrease
Syonymous is the adjectival form of synonym.
You've spelled the word "synonymous" correctly :)
Posterior?
extend
Synonymous means having the same meaning as another word or phrase. Aggression is often believed to be synonymous with violence.
Words that are not synonymous with the word 'preposterous' include:appropriatecorrectfairjustlogicalproperrationalreasonablesensiblesoundtruevalid
I believe you are trying to spell "synonymous" (same meaning).
synonymous.
avarice