Melody (noun)

1. A sequence of single notes or pitches perceived as a cohesive whole; a tune.
2. The principal part in a harmonic composition; the air.
3. The audible characteristics of a particular sound or voice, as determined by the frequency and amplitude of the sound waves produced.
4. A pleasing succession or arrangement of sounds.
5. A rhythmical succession of single tones producing a distinct musical phrase or idea.

Origin:

From middle english melodie, from old french melodie, from late latin melodia, from ancient greek μελῳδία (melōidía), from μέλος (mélos, “song, melody”) + ἀοιδή (aoidḗ, “singing, chant”).

Examples:

1. The melody of the song was so catchy that it stayed in my head all day.
2. The melody played by the pianist was haunting and beautiful.
3. Her voice had a lovely melody that was both soothing and captivating.
4. The melody of the orchestra was a perfect accompaniment to the ballet.
5. The melody of the piece was complex and challenging for the musicians to play.