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
"High-quality and luxury are often synonymous in the minds of consumers looking for premium products."
I believe you are trying to spell "synonymous" (same meaning).
avarice
Well-being.
synonymous.