Since its a sibling, and siblings tend to be in a person's close circle of people, informal speech is used.
Answer:
these are some examples:
Phonetics - the study of speech sounds in their physical aspects.
Phonology - the study of speech sounds in their cognitive aspects.
Morphology - the study of the formation of words.
Syntax - the study of the formation of sentences.
Semantics - the study of meaning.
Pragmatics - the study of language use.
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