The basic function the expression 'you know' serves in conversational discourse is said to be that of a pragmatic particle used when the speaker wants the addressee to accept as mutual knowledge (or at least be cooperative with respect to) the propositional content of his utterance. The fact that 'you know' is even used when the addressee is assumed not to know what the speaker is talking about, suggests that it functions at the deference level of politeness, as a striving towards attaining a camaraderie relationship between speaker and hearer. 'You know' is found to be more often used by women than by men in spontaneous conversation, and the manner in which it is used is significantly different from male usage. Ontogenetically, the age of four seems to be crucial for initial steps to use and master pragmatic particles including 'you know'. Data for the study were obtained from tape-recorded conversations and interviews.