Linguistics is the scientific study of language.  Its sub-fields include:

• phonetics: the study of speech sounds
• phonology: the study of how sounds are organized in natural languages.
• morphology: the study of word structure
• syntax: the study of how words are arranged into phrases and sentences
• semantics: the study of meaning
• pragmatics: the study of how language is used in social contexts.

Other sub-fields result from the intersection of linguistics with other fields:

• Historical linguistics is the study of how language changes over time.
• Sociolinguistics is the study of language in society.
• Psycholinguistics studies how language is processed in the mind.
• Neurolinguistics studies how the brain encodes language.
• Computational linguistics studies how computers and computational models can be used to model and process natural language.