Ancient Greek, like modern English, possesses separate word-groups, from different roots, for laughter and smiling. This is not true of all languages: some (such as Latin and its Romance descendants) use closely related word-groups, while others make no lexical distinction at all. Whether linguistically or corporeally, the relationship between laughter and smiles is intricate. Distinguishable in principle, the two can overlap or shade into one another. In physiological terms, laughter paradigmatically involves staccato vocalisation and a tautening of facial musculature (with mouth opened to facilitate intensified breathing), while smiling is a facial but not vocal form of expression. Although such details are not always made explicit, there is no doubt that they form the basis of the distinction between γελᾶν (laugh) and μειδ(ι)ᾶν (smile). It is possible to hear without seeing someone laugh, as the insomniac Odysseus overhears the maidservants' indecent mirth in a scene of thrilling psychological tension at Odyssey 20.5–8. But one can only see (or imagine one sees) a smile – or at any rate, by poetic extension, picture one on a symbolic ‘inner’ face, as Homer does. Despite the difference between laughter as facio-vocal and smiling as purely facial, there are varieties and gradations of both behaviours, and these complicate classification. In particular, the visual impressions of laughing and smiling can be thought of as forming a (blurred) continuum.

Greek writers presuppose a basic distinction, as well as expressive affinities (but not identity), between γελᾶν and μειδ(ι)ᾶν.