Classroom communication can be described as

Concept: In communication studies, discourse means language in use — connected, purposeful talk or text produced by participants in a social setting and organised by shared conventions of turn-taking, topic control, role and register. A discourse is defined by the whole exchange among its participants and by the meanings they jointly build, not by any single isolated utterance.

Applying it here: A classroom is precisely such a setting. Teacher and learners exchange connected, purposeful language in institutionally defined roles, and the talk follows recognised structures — most typically the initiation–response–feedback (IRF) sequence described by Sinclair and Coulthard (1975), in which the teacher initiates, a learner responds and the teacher gives feedback. Because the exchange is continuous, rule-governed, role-bound and meaning-making, classroom communication is described as discourse; "classroom discourse" is the standard term for it in educational linguistics.

Contrasting the other terms:

• Exploration names an open-ended enquiry activity — searching unfamiliar material to find what possibilities it holds. It describes a mode of investigation, not a category of language exchange.

• Institutionalisation names the process by which a practice hardens into the fixed rules, roles and structures of a formal organisation. It is a property of the school as an institution, not a description of the communication carried on inside it.

• Unsignified narration names telling to which no shared sign or meaning-code has been attached. Classroom communication depends on meanings that teacher and learners jointly recognise, so it cannot be unsignified.

Result: Classroom communication is best described as discourse.