Etymology: The origin of the English word harmony is the Greek word "harmos" which means to join.

Definition
·  harmony (noun) The word harmony means pleasant musical
   sound made by different notes being played or sung at the same
   time.
·  harmonious (adjective) - ious
·   harmoniously (adverb) - iously
·   harmonise (verb), UK - ise
·   harmonize (verb), US - ize