chemical reaction [chemical reactions](process in which chemical substances are changed into others) noun [UK: ˈke.mɪk.l̩ rɪ.ˈæk.ʃn̩] [US: ˈke.mək.l̩ ri.ˈæk.ʃn̩]
combustion [combustions](similar process where two chemicals are combined) noun [UK: kəm.ˈbʌs.tʃən] [US: kəm.ˈbəs.tʃən]