Genelde, genellikle, çoğunlukla
They all means : usually.
But it seems that there are differences between them. Which ones, please ?
Genelde means "in general" if we exactly translate which means generally,
Genellikle means usually.
They don't differ from each other, genelde and genellikle can be used for same thing. Don't hesitate to use it.
Çoğunlukla means mostly.
Somebody told here çoğunlukla means often/frequently but it's wrong. Sık sık/sıklıkla means often/frequently. Çoğunlukla means absolutely "mostly".