A coherent succession of pitches. - Harvard Dictionary of Music
PITCH or NOTE or TONE: when referred to in melody, these are the individual sounds that comprise a melody. When you hum or sing or play a melody, you are performing a series of pitches/notes/tones in succession.
SCALE: a pattern of notes used to create a melody (this is what keeps melodies sounding comfortable, familiar, and predictable rather than random and unpredictable). Most musical scales are in MAJOR (sound happy) or MINOR (sound sad or maybe angry or scary).
https://www.researchgate.net/publication/281633714_Melodic_Contour_Training_and_Its_Effect_on_Speech_in_Noise_Consonant_Discrimination_and_Prosody_Perception_for_Cochlear_Implant_Recipients
MELODIC CONTOUR: refers to the shape of the melody - like drawing an arrow to accompany the direction of the melody. Melodies can go up or down or stay flat and repeat the same note. When you sing along to a song, you’re creating a melodic contour with your voice - a visual representation (drawing a line higher as the melody goes higher, or lower as the melody drops lower) is a great way to communicate a lot of information about the piece of music quickly.
STEPWISE MOTION: is when melodies go one note up or down a scale. This sounds simpler, easier, and more stable.
LEAP MOTION: is when melodies go multiple notes up or down a scale. This sound more unexpected, energized, and dramatic.
Source : kaitlinbove.com