Linguistics is the scientific study of language. The areas of linguistic analysis are syntax (rules governing the structure of sentences), semantics (meaning), morphology (structure of words), phonetics (speech sounds and equivalent gestures in sign languages), phonology (the abstract sound system of a particular language, and analogous systems of sign languages), and pragmatics (how the context of use contributes to meaning). Subdisciplines such as biolinguistics (the study of the biological variables and evolution of language) and psycholinguistics (the study of psychological factors in human language) bridge many of these divisions.

Linguistics encompasses many branches and subfields that span both theoretical and practical applications. Theoretical linguistics is concerned with understanding the universal and fundamental nature of language and developing a general theoretical framework for describing it. Applied linguistics seeks to utilize the scientific findings of the study of language for practical purposes, such as developing methods of improving language education and literacy.

Linguistic features may be studied through a variety of perspectives: synchronically (by describing the structure of a language at a specific point in time) or diachronically (through the historical development of a language over a period of time), in monolinguals or in multilinguals, among children or among adults, in terms of how it is being learnt or how it was acquired, as abstract objects or as cognitive structures, through written texts or through oral elicitation, and finally through mechanical data collection or practical fieldwork.

Linguistics emerged from the field of philology, of which some branches are more qualitative and holistic in approach. Today, philology and linguistics are variably described as related fields, subdisciplines, or separate fields of language study, but, by and large, linguistics can be seen as an umbrella term. Linguistics is also related to the philosophy of language, stylistics, rhetoric, semiotics, lexicography, and translation.

Historical linguistics is the study of how language changes over history, particularly with regard to a specific language or a group of languages. Western trends in historical linguistics date back to roughly the late 18th century, when the discipline grew out of philology, the study of ancient texts and oral traditions.

Historical linguistics emerged as one of the first few sub-disciplines in the field, and was most widely practised during the late 19th century. Despite a shift in focus in the 20th century towards formalism and generative grammar, which studies the universal properties of language, historical research today still remains a significant field of linguistic inquiry. Subfields of the discipline include language change and grammaticalization.

Historical linguistics studies language change either diachronically (through a comparison of different time periods in the past and present) or in a synchronic manner (by observing developments between different variations that exist within the current linguistic stage of a language).

At first, historical linguistics was the cornerstone of comparative linguistics, which involves a study of the relationship between different languages. At that time, scholars of historical linguistics were only concerned with creating different categories of language families, and reconstructing prehistoric proto-languages by using both the comparative method and the method of internal reconstruction. Internal reconstruction is the method by which an element that contains a certain meaning is re-used in different contexts or environments where there is a variation in either sound or analogy.^{[better source needed]}