combustionn.

combustion (n.)early 15c., from Old French combustion (13c.), from Latin combustionem (nominative combustio) "a burning," noun of action from past participle stem of Latin comburere "to burn up, consume," from com-, intensive prefix (see com-), + *burere, faulty separation of amburere "to burn around," actually ambi-urere, from urere "to burn, singe," from PIE root *eus- "to burn" (see ember).