Ming from Agents of Speech explains that back and forth conversations don't need to be long. Even one or two turns count, and nonverbal exchanges like pointing, giving, or smiling work too. What matters is the child's language level, not a formal definition.
A back and forth conversation is defined by you. At what language level are you talking about? If a child is at two words and they can answer some questions, then you might ask them a question, they might answer you back, and it might go back and forth one or two times. That's already back and forth. If your child is nonverbal, just giving you something, showing you something, tapping you, giving you a gesture, and then you answer back and they smile at you and whatever, that's already back and forth. There's no dictionary term. Like in our industry, we don't have a term called back and forth conversation. There are only what we call language functions.
