Well you need to speak for you to be able to communicate. Speaking is one of the ways used for communication. =p

Speaking (and listening to it) is only one way of communicating. Others are: Writing (and reading). Body language: the way you look (/you are seen), move, and gesture. And concludive acts like sending something to someone. Where the other person can act (/react) upon. Doing nothing at all also is some form of communication. When you are supposed to do something and you don't. This may be interpreted by your partner. The 'Model of Communication' has a 'sender' and a 'receiver'. The sender codes (/forms) messages with his (or her) pool of language (like a dictionary), depending on education and experience. Then the information is sent. On the 'channel' it can be changed and corrupted (/damaged). Like on a bad phone line. Then the receiver 'reads' the message. Decoding it using the available language pool. That's the reason why messages not always are understood as intended. But surprisingly often I understand what might have been meant...