Communication

The sending and receiving of information, ideas,feelings, or messages.

We transmit messages of all kinds by speech, the written word, Morse code, semaphore flags, Braille, facial expressions, gestures, art, music, dance, the clothes we wear, etc.

Language

Language is a system of abstract symbols and rule-governed structures,  the specific conventions of which are learned.

Language may be sounds, written letters, etc.

Speech

Speech is the oral expression of language.

Difference from language:

Parrots can produce speech but not language.

Mute children can produce language without speech through signing.

Echolalia

Pragmatics