(linguistics) The ability to comprehend information and understand spoken language (or sign language). It may include understanding of the vocabulary and concepts presented, short-term memory and sequencing information.

A language that is not widely or officially spoken in a particular place. / A language that is not one's native tongue.

(linguistics) a pidgin language

(linguistics, translation studies) The language from which a translation is done. / (computing) The language of the source code to be compiled.

(linguistics) The language a learner is attempting to acquire. / (linguistics, translation studies) The language into which a translation is done.

Profanity.

A conceptual barrier to effective communication, occurring when people who speak different languages attempt to communicate with each other.

constructed language / formal language / computer language

Any language—whether a human language, a programming language, or markup language—that is not a natural language.

(computer languages) A programming language in which the source code of programs is composed of mnemonic instructions, each of which corresponds directly to a machine instruction for a particular processor.