What is the definition of melody harmony and rhythm?

Melody is the succession of single tones of varying pitch. Melody is the linear aspect of music, in contrast to harmony, the chordal aspect, which results from the simultaneous sounding of tones. Melody must be considered with rhythm.

Rhythm is the the basic temporal element of music, concerned with duration and with stresses or accents whether irregular or organized into regular patternings.

Harmony is the simultaneous sounding of two or more tones and, especially, the study of chords and their relations. Harmony was the last in the development of what may be considered the basic elements of modern music-harmony, melody, rhythm, and tone.