Diction not only includes patterns of speech, Diction can also mean the lack of a spoken word: Silence. Silence is a frequently overlooked, but powerful, meme to employ in an effective life stage performance.
The whisper, the hushed tone, and the silent look are all incredibly powerful moments in performance when employed by a properly trained actor.
You can also be daring and bring to the empty space a completely silent performance. Audiences will immediately get edgy in the quiet as every cough and fart and giggle from them become part of the hubbub surrounding the silent performance.
A silent performance means a lack of recognizable speech. A silent performance can be quite noisy with the opening of creaky doors, the shuffling of leather soles across a rough stage and the flappy sound of sheer curtains blowing across an open window.
Silent performances challenge actors to find a way to express a thought from the body in situ instead of relying of vocalization tricks. Oftentimes a silent performer is more memorable, and infinitely more human, than an actor who relies on voice alone.