Instead of human language, animals possess their own communication systems that allow them to transmit information.
Scientists often define animal communication as the provision of information (via a signal) by a sender to a receiver, and subsequent use of this information by the receiver in deciding how or whether to respond. These signals occur in many forms
Dolphins produce a vast number of signals in a variety of modes. The different channels or modes include: vocal signals, non-vocal auditory signals, visual signals and tactile signals.
the most obvious form of communication that dolphins use is vocal signals. Dolphins also produce a number of non-vocal sounds that they use for communication. Non-vocal in this sense means any sound that is not produced using the organs within a dolphin’s vocal area that nonetheless produce sound.
Some studies suggest that children with problems to speak improve their skills if they interact with dolphins. This therapy is also used with Down's Syndrome and for example in Spain there are two centers specialized in this matter.
Dolphins help US military by finding mines and bombs under the sea and ocean.