Linguistic determinism is the concept that language and its structures limit and determine human knowledge or thought, as well as thought processes such as categorization, memory, and perception. The term implies that people's native languages will affect their thought process and therefore people will have different thought processes based on their mother tongues.

Linguistic determinism is the strong form of linguistic relativism (popularly known as the Sapir–Whorf hypothesis), which argues that individuals experience the world based on the structure of the language they habitually use. Since the 20th century, linguistic determinism has largely been discredited by studies and abandoned within linguistics, cognitive science, and related fields.

The Sapir-Whorf hypothesis branches out into two theories: linguistic determinism and linguistic relativity. Linguistic determinism is viewed as the stronger form – because language is viewed as a complete barrier, a person is stuck with the perspective that the language enforces – while linguistic relativity is perceived as a weaker form of the theory because language is discussed as a lens through which life can be focused, but the lens can be changed, and perspectives can be changed along with it.

The term "Sapir–Whorf hypothesis" is considered a misnomer by linguists and academics, because Edward Sapir and Benjamin Lee Whorf never co-authored any works (however, Whorf had studied under Sapir at Yale University ), and never stated their ideas in terms of a hypothesis. The distinction between a weak and a strong version of this hypothesis is also a later invention; Sapir and Whorf never set up such a dichotomy, although often in their writings their views are expressed in stronger or weaker terms. The two linguists were nevertheless among the first to formulate the principle of linguistic relativity.

While Sapir exercised the idea that language is essential to understanding one's worldview and that difference in language implies a difference in social reality, he never directly explored how language affects thought, although significant traces of the linguistic relativity principle underlie his perception of language.

Whorf explored Sapir's concept further and reformulated Sapir's thought in his essay "Science and Linguistics". In Whorf's more radical view, the relationship between language and culture played a crucial role in the perception of reality. The formulation of thoughts, according to Whorf, is not a conscious, independent process, rather, thoughts are determined by the specific grammar and vocabulary of the language in which ideas are expressed. The world, as each individual views it, is, therefore, organized and rationalized through language; because language is the way thoughts are expressed, the language can also shape thoughts.

Linguistic determinism and linguistic relativity are heavily debated and researched topics among academics, like linguists Guy Deutscher and Eric Lenneburg, psychologists such as Peter Gordon and Steven Pinker, and even philosophers like Friedrich Nietzsche. There are critiques and support for both theories as outlined in research among Guugu-Yimidhirr, Hopi, and Pirahã speakers.

Whorf's conclusion was largely based upon a close examination and extensive study of the Native American Hopi language spoken among natives of southwestern North America. During earlier years, Whorf published a number of essays in which he analyzed various linguistic aspects of Hopi. For example, a work called "An American Indian model of the universe" (1936) explores the implications of the Hopi verb system concerning the conception of space and time.