IPA: /ˌkoʊ.ə.lɪ.fɪˈkeɪ.ʃən/
KK: /koʊəˈlɪfɪˌkeɪʃən/
The process through which plant material is transformed into coal over a long period, involving compression and hardening.
The coalification of ancient forests took millions of years to create the coal we use today.
Coalification is formed from "coal" (from Old English *cāle*, meaning a black combustible material) and "-ification" (from Latin *-ificare*, meaning to make or to cause). The term describes the process of transforming organic material into coal.
Think of the process of 'making coal' — 'coal' refers to the combustible material, and '-ification' means to make or cause something to happen.