Communication Styles

We're commonly told to make sure that our characters speak their dialogue in a distinctive voice. While this is good advice-- everyone does have personal speech patterns-- communication involves a lot more than talking. Behavioural scientists estimate up to 80% of human communication is nonverbal, and that's not just body language. We tell each other volumes with our clothing, our tone of voice, what we choose to remember or ignore, or actions, such as touch.
Each of us has a preferred style of communication. Some of us prefer to verbalise our feelings directly, some take an indirect approach. Some people feel less comfortable with words, and prefer physical gestures instead.
Thinking about how a character communicates means considering the whole package-- their preferred communication style, their nonverbal communication style, and their speech (and yes, if you're writing a deaf character, signing is speech) to capture the way that individual interacts with the other characters and their world.