In linguistics, grammaticalization (also known as grammatization, grammaticization) is a process by which words representing objects and actions (i.e. nouns and verbs) transform through sound change and language migration to become grammatical objects (affixes and prepositions, etc.). Grammaticalization is a powerful aspect of language, as it creates new function words within language, by separating functions from their original inflectional and bound constructions (i.e. from content words). It is a field of research in historical linguistics, in the wider study of language change, which focuses on a particular process of lexical and grammatical change. For an understanding of this process, a distinction needs to be made between lexical items, or content words, which carry specific lexical meaning, and grammatical items, or function words, with little or no lexical meaning which serve to express grammatical relationships between the different words within an utterance. Specifically, "the change whereby lexical terms and constructions come in certain linguistic contexts to serve grammatical functions, and, once grammaticalized, continue to develop new grammatical functions".[1] Simply said, grammaticalization is the process in which a lexical word or a word cluster loses some or all of its lexical meaning and starts to fulfil a more grammatical function. It means that nouns and verbs which carry certain lexical meaning develop over time into grammatical items such as auxiliaries, case markers, inflections and sentence connectives. A well-known example of grammaticalization is that of the process in which the lexical cluster let us, for example in the sentence "let us go", is reduced to a single word let's as in the sentence "let's you and me fight". The phrase has lost its lexical meaning of "allow us" and has changed into an auxiliary, while the pronoun 'us' reduced first to a suffix and then to an unanalyzed phoneme.

Many languages do not grammaticalize all three categories. For instance, English has past and non-past ("present"); other languages may have future and non-future. In some languages, there is not a single past or future tense, but finer divisions of time, such as proximal vs. distant future, experienced vs. ancestral past, or past and present today vs. before and after today. Some attested tenses: Future tenses. Immediate future: right now Near future: soon Hodiernal future: later today Vespertine future: this evening[citation needed] Post-hodiernal: after today Crastinal: tomorrow Remote future, distant future Posterior tense (relative future tense) Nonfuture tense: refers to either the present or the past, but does not clearly specify which. Contrasts with future. Present tense Still tense:[citation needed] indicates a situation held to be the case, at or immediately before the utterance Nonpast tense: refers to either the present or the future, but does not clearly specify which. Contrasts with past. Past tenses. Some languages have different past tenses to indicate how far into the past we are talking about. Immediate past: very recent past, just now Recent past: in the last few days/weeks/months (conception varies) Nonrecent past: contrasts with recent past Hodiernal past: earlier today Matutinal past: this morning[citation needed] Prehodiernal: before today Hesternal: yesterday or early, but not remote Prehesternal: before yesterday Remote past: more than a few days/weeks/months ago (conception varies) Nonremote past: contrasts with remote past Historical Past: shows that the action/state was part of an event in the past Ancestral past, legendary past General past: the entire past conceived as a whole Anterior tense (relative past tense)