Really all of these are shorthand for something much more fundamental around ratios and how these are experienced by the human body at different frequencies.
Harmony is shorthand for ratios at audible frequencies (~20-20,000 Hz) as they are quite directly picked up in the ear. Rhythm is shorthand for ratios expressed at much lower frequencies (~0.1-10Hz) which the body interprets with relation to its own functions (heartbeat, walking, dancing, speech). Melody is a combination of harmonic and rhythmic ratios in a way the human body has been trained to hear as a 'voice'.
Harmony is shorthand for ratios at audible frequencies (~20-20,000 Hz) as they are quite directly picked up in the ear. Rhythm is shorthand for ratios expressed at much lower frequencies (~0.1-10Hz) which the body interprets with relation to its own functions (heartbeat, walking, dancing, speech). Melody is a combination of harmonic and rhythmic ratios in a way the human body has been trained to hear as a 'voice'.