A cant is the jargon or language of a group, often employed to exclude or mislead people outside the group. It may also be called a cryptolect, argot, pseudo-language, anti-language or secret language. Each term differs slightly in meaning; their uses are inconsistent.

There are two main schools of thought on the origin of the word cant:

An argot (English: /ˈɑːrɡoʊ/; from French argot [aʁɡo] 'slang') is a language used by various groups to prevent outsiders from understanding their conversations. The term argot is also used to refer to the informal specialized vocabulary from a particular field of study, occupation, or hobby, in which sense it overlaps with jargon.

In his 1862 novel Les Misérables, Victor Hugo refers to that argot as both "the language of the dark" and "the language of misery".

The earliest known record of the term argot in this context was in a 1628 document. The word was probably derived from the contemporary name les argotiers, given to a group of thieves at that time.

Under the strictest definition, an argot is a proper language with its own grammatical system. Such complete secret languages are rare because the speakers usually have some public language in common, on which the argot is largely based. Such argots are lexically divergent forms of a particular language, with a part of its vocabulary replaced by words unknown to the larger public; argot used in this sense is synonymous with cant. For example, argot in this sense is used for systems such as verlan and louchébem, which retain French syntax and apply transformations only to individual words (and often only to a certain subset of words, such as nouns, or semantic content words). Such systems are examples of argots à clef, or "coded argots".

Specific words can go from argot into everyday speech or the other way. For example, modern French loufoque 'crazy', 'goofy', now common usage, originated in the louchébem transformation of Fr. fou 'crazy'.

In the field of medicine, physicians have been said to have their own spoken argot, cant, or slang, which incorporates commonly understood abbreviations and acronyms, frequently used technical colloquialisms, and much everyday professional slang (that may or may not be institutionally or geographically localized). While many of these colloquialisms may prove impenetrable to most lay people, few seem to be specifically designed to conceal meaning from patients (perhaps because standard medical terminology would usually suffice anyway).