Predominantly means for the most part, and more than anything else. Predominantly rural, predominantly female, predominantly white.
It claims a majority rather than the whole, which is what makes it useful in describing populations without overstating. It is a shade more formal than mostly and appears constantly in official descriptions.
1adverbpredominantlyFor the most part, and more than anything else.
“The audience was predominantly made up of students and young families.”
predominantly is a degree.
Medieval Latin
praedominans
Middle French
prédominant
English
predominant
English, today
predominantly
From predominant + -ly. predominant comes from Middle French prédominant, ultimately from Medieval Latin praedominans. by surface analysis, en + pre- + dominant.
Etymology from Wiktionary, CC BY-SA