Melody

An in interval is the distnace in pitch between two notes.

The smallest interval is a semitone for example C to C#

A musical phrase is a short musical passage.
It is like a spoken sentence.
You can hear a 'breath' at the end of a phrase.

Imitation

- Where a melody in one part is repeated again, later.
- It overlaps themelody in the first part.
- Useful as a textural device.
- Sometimes imitations contain slight changes such as:
1. Changing the octave 
2. Adding ornaments
3. Playing the notes f different duration.

A riff, ostinato or loop are repeated pattern of notes.

Ostinatos - classical music, being a repeating pattern of notes or rhythms.
Riff - Pop music, being a recognisiable pattern of notes.
Loop - Contemporary dance music, being a patteren which appears as a cycle.

A sequence is a pattern of notes which goes up or down in itch every time it is repeated. 

A fill is a short flourish used to fill a gap between phrases - often played on drums.

A break is an extended instrumental section in dance music or a solo in pop and jass - usually improvised.

A hook is a short catchy melodic idea ddesigned to be memorable.

Ornaments are decorative notes which embellish a melody:

Trill
Formed by quickly playing he note and the note above it alternatively.

Mordent
Formed by playing the note, the note abve then back to the first note.

Grace note
A single note ornament such as acciaccatura and appoggiatura:

Acciaccatura: 
Played as quickly as possible before the note that follows. Often called a crush note. 

Appoggiatura 
Leans on the main note, taking part of its value.