Penelope Brown and Stephen Levinson's Politeness Theory
negative politeness strategies: strategies that are performed to avoid offense through deference
positive politeness strategies: strategies that are performed to avoid offense by emphasizing friendliness.
negative face: the wish to be unimpeded by others in one’s actions.
positive face: the wish or desire to gain approval of others.
Speech Acts become acts of negative politeness when they match the negative face want of either the speaker or the addressee. These include emphasis of social distance, use of apologies, formal language, deference etc. Those speech acts attending to the positive face want of a member are considered to be acts of positive politeness, including offer of friendship, compliments, showing direct interest, heartily expressions etc.