Contexts of communication are best thought of as a way to focus on certain communication processes and effects. Communication context boundaries are fluid. Thus, we can see interpersonal and group communication in organizations. Gender communication occurs whenever people of different sexes communicate. We can have mass communications to individuals, group, and organizations.
Some people facetiously say intrapersonal communication exists when someone talks to themselves.
It's more accurate to define intrapersonal communication as thinking. While thinking normally falls within the purview of psychology we can recognize that we often think, plan, contemplate, and strategize about communication past, present, and future. It is legitimate to study the cognitive aspects of communication processes. So, even if some people call those cognitive aspects of communication thinking, it can be helpful to recognize the context of intrapersonal communication, thereby legitimating an avenue of communication research. Each page linked to below contains a summary of a theory and citations to related work.