One speech for all. A brief rule about the word: to speak "both in the senate and to anyone whoever he may be" (καὶ ἐν συγκλήτῳ καὶ πρὸς πάνθ’ ὁντινοῦν) alike "with propriety" (κοσμίως), without "affectation" (περιτράνως — "over-loud," with ostentatious pathos). One measure of speech for the highest assembly and for a private person is the mark that the speaker does not tailor himself to the addressee but keeps his own order (cf. 6.30 — not to be "Caesarised"; one manner before all).
Sound speech. The positive norm is TERMto "use sound speech" (ὑγιεῖ λόγῳ): speech without disease — without affectation, flattery, or ambiguity; a word that answers to thought and deed. Rogovin's "let your speech be truthful" rightly catches ὑγιής as "uncorrupted." The discipline is action: speech is a deed among people, and "sound" discourse is a part of social virtue (cf. 01-07 — from Rusticus: to write and speak plainly; 11.15 — nothing is more shameful than pretence). The strict term by the word is λόγος (λόγῳ). The governing discipline is action (how to keep one's word among people).