From Diogenes Laertius 7.56-59, with addenda.
[1] This definition is Aristotelian (On Interpretation 16b26).
[2] cf. beta 335.
[3] These lines reproduce Diog.Laert. 7.57 in a slightly different way and their content is Stoic.
[4] See Diog.Laert. 7.59 (= SVF 3.24). By "Hellenism" is meant the use of good Greek style and diction which is in accordance with grammar; clarity is an expression (le/cis) easily understandable; brevity is a speech which includes no more words than are necessary for the sake of clarification of the thing under discussion; propriety is a speech which is appropriate to the thing under discussion. With regard to the last type of excellence of discourse, there must be a mistake in the Suda text. The Diog.Laert. passage reads kataskeuh/, "correct style" or "elaboration", which has the right sense. In fact, a)poskeuh/ ("filth" or "ordure") does not fit the meaning of a specific excellence of discourse unless it is taken with its meaning of "stuff, things that fill in". On these "best qualities of discourse", see Atherton (1993) 89-92.
[5] Aristophanes, Peace 146-147, with comment from the scholia there. "Plot" is the conventional translation of logos in dramatic contexts, i.e. the main story in the narrative or drama.
[6] chi 569.