The textbook classifies human communication into two broad types:

• Intra-personal communication: “The part of communication in which self of a human being is involved only and the communication is confined to one human entity. This means that all the elements which come into action in a given piece of communication are located within the self of an individual. A message originating from source part of the brain travels through the channel of nerves to reach another location, however close it may be to the point of origin.” Examples: thinking, reasoning, meditation, monologue, and dreaming.
• Inter-personal communication: Involves two or more individuals, and is further classified into interpersonal (one-to-one), group communication, organisational communication, and mass communication.

The key distinguishing criterion is that in intra-personal communication, all elements — source, encoder, channel, decoder, and receiver — exist within the same person. No external communication partner is required.