Gricean maxims

In semantics/pragmatics, the Gricean maxims are communicative principles that were proposed by H.P. Grice as an elaboration of his Cooperative Principle. He distinguished four categories, with several submaxims (Grice 1975):

Quantity 1 Make your contribution as informative as is required (for the current purposes of the exchange). 2 Do not make your contribution more informative than is required.

Quality: ‘Try to make your contribution one that is true’ 1 Do not say what you believe to be false. 2 Do not say that for which you lack adequate evidence.

Relevance: ‘Be relevant’

Manner: ‘Be perspicuous’ 1 Avoid obscurity of expression. 2 Avoid ambiguity. 3 Be brief (avoid unnecessary prolixity). 4 Be orderly.

A speaker who is assumed to be cooperative, can be interpreted as meaning more than he literally says, either by following the maxims or by intentionally flouting them.

Example
A: Miss X produced a series of sounds that corresponded closely with the score of ‘Home Sweet Home.’

By choosing this prolix formulation (instead of the simple Miss X sang ‘Home Sweet Home’) A violates the Manner maxim, but because of cooperativity, we are invited to assume that he must have had a reason for this, wanting to implicate (i.e. wanting his utterance to have the implicature) that there was something seriously wrong with Miss X’s singing. In later work, reductions of the maxims have been proposed, yielding two main directions of thought, the Neo-Gricean theory (Atlas and Levinson 1981, Horn 1984) and the Relevance theory (Sperber and Wilson 1986).

Link
Utrecht Lexicon of Linguistics