It's spelled advantage, a-d-v-a-n-t-a-g-e, pronounced /ədˈvɑːntɪdʒ/ or /ədˈvæntɪdʒ/. The word is a noun.
The unstressed first vowel is /ə/, and the final e after g is silent in the ending /ɪdʒ/, yet it must still be written.
Spelled advantage, pronounced /ədˈvɑːntɪdʒ/ or /ədˈvæntɪdʒ/. Both transcriptions appear side by side in the dictionary entry.
The word is the noun advantage. Example: This seat has a good advantage.
The first vowel is unstressed /ə/, a weak schwa sound, so the opening syllable gives no spelling clue by ear. Trust the pattern a-d-v instead.
One small trap: the final e after g is silent in speech, since the word ends in the single sound /ɪdʒ/, but it must still be written. Leaving it off produces the common misspelling advantag.