What is the meaning of Harmony?

Agreement or accord.

A pleasing combination of elements, or arrangement of sounds.

The academic study of chords.

Two or more notes played simultaneously to produce a chord.

The relationship between two distinct musical pitches (musical pitches being frequencies of vibration which produce audible sound) played simultaneously.

A literary work which brings together or arranges systematically parallel passages of historians respecting the same events, and shows their agreement or consistency.

Source: wiktionary.org