Language, dialect, tongue, speech, idiom are comparable when they denote a body or system of words and phrases used by a large community (as of a region) or by a people, a nation, or a group of nations.
Language may be used as a general term for a body of communicative symbols whether it is made up of words, or of sounds, gestures, and facial expressions, or of visual signals (as a code of lights, smoke, or flags), or of electrical impulses in a computer. However, in its ordinary and specific sense the term refers to a body of words that by long use by the population of a widespread territory has become the means whereby the ideas or feelings of the individual members of that population are communicated or expressed. The term suggests some degree of stability in behavior (as in vocabulary, pronunciation, and grammaticality); it usually connotes the existence of a standard determined by the usage of educated writers and speakers.
But language is also applied to a body of words and phrases that is peculiar to an art, a science, a profession, or a class and that, however well understood by others of the community, is not generally adopted by them.
Dialect (see also DIALECT 1 ) may denote a form of language which is clearly distinguishable from other forms by marked differences and an identity of its own. More often it refers to a variant of a recognized language, restricted to a limited area and not entirely unintelligible to speakers of the language of which it is a phase. Tongue and speech both call attention to the spoken rather than written communication.
Tongue differs from language chiefly in its being applicable to a dialect, a patois, an argot ((for these terms, see DIALECT 1 ))as well as to the standard form of a language.
Speech, with rare exceptions, means spoken language, or (as in modern technical use) language as it is spoken.
Idiom suggests reference to a country or sometimes to a province or section of a country with its own peculiar and distinctive tongue. Idiom also may apply to private or peculiar language (as of a particular writer, class, literary school, or group).