log- / loq- "speak"

dialogue dia- “through”

monologue mono- “one”

monochrome chrome “color”

catalogue cata- “down”

prologue pro- “before”

apology apo- “away”

apologize

eulogy eu- “good”

eugenics gen- “birth” gene, generation 

euthanasia than- “death”

eloquent ex- “out”

grandiloquent

colloquial col- “together”

soliloquy sol- “self”