Intonation

Intonation is a complex system of meaning communicated through the rise and fall of a speaker’s voice. Intonation refers to how the voice can change pitch to convey meaning. In essence, intonation replaces punctuation in spoken language. English speakers use it to communicate many different types of meaning:
1. grammatical meaning e.g. different types of questions and statements
2. status of information e.g. main or subordinate, finished or unfinished
3. attitude e.g. whether we’re certain or not, have doubts or reservations
4. feeling e.g. whether we’re confident, happy, enthusiastic, sad or bored etc.
5. relational e.g. how ‘open’, friendly or ‘closed’ we are towards a listener

Sources:

Bolinger, Dwight, L. (1951). "Intonation: Levels Versus Configurations"

Brazil, D., Coulthard, M., Johns, C. (1980). Discourse intonation and language teaching. Longman