See our pages: Verbal Communication and Non-Verbal Communication for more information.
When two or more people are in the same place and are aware of each other's presence, then communication is taking place, no matter how subtle or unintentional.
Without speech, an observer may be using cues of posture, facial expression, and dress to form an impression of the other's role, emotional state, personality and/or intentions. Although no communication may be intended, people receive messages through such forms of non-verbal behaviour.