IPA: /prɪˈdɒmɪnəntli/
KK: /prɪˈdɑː.mɪ.nənt.li/
In a way that is the most common or frequent; mainly or mostly.
The population in the city is predominantly young adults.
Predominantly → It is formed from "pre-" (meaning before) and "dominari" (meaning to rule or dominate) and the suffix "-ly" (meaning in a manner). The word "predominantly" means in a manner that rules or is prevalent before others, indicating a primary or major influence.
Think of something that 'rules' ('dominari') 'before' ('pre-') everything else — that's why predominantly means mainly or primarily.