Inter-personal communication is most often considered as

Inter-personal communication is most often considered dyadic, an exchange between two people who send and receive in direct, mutual contact.

The two parties take turns as sender and receiver, giving immediate feedback in a close, face-to-face relationship.

Reading it as within oneself describes intrapersonal communication, the inner talk of a single mind, not exchange between two.

Naming it many-to-many points to group or network communication, well beyond the two-person core of the interpersonal form.

Treating it as one-to-huge masses describes mass communication, where a single source reaches a vast scattered audience.

The two-person, feedback-rich pattern is exactly what marks interpersonal communication as dyadic.