Is there a formal way of writing about language in a play, its uses and how it is constructed?

I am currently engaged in doing a thesis on a specific play. I do not have any formal degree in English, so I guess, I am figuring out things as I go. One phrase that pops up when a play is critiqued is that the language a 'symmetry'. What does this phrase mean? What I would like to demonstrate is how language works in the world of the play, Does 'Symmetry' imply shape, for example two characters are in dialogue with each other, they talk about one topic, end that topic and move on to another topic or related topic, is that what symmetry implies? in the world of a play when talking about langauge. Is it the strings of conversations and their connectivity or what?