Homophony is music in which the top line has a dominant melody, and all the voices accompany it with chordss in the same rhythm. Many hymn harmonisations are homophonic.
Homophony is contrasted with polyphony (in which each voice is contrapuntally independent and equal) and monophony (in which there is only one voice).
Homophony is sometimes used less accurately to refer to music with a melody and rhythmically independent accompaniment, which is actually monody.
See Texture (music)