Sign languages are the names given to languages that use the visual channel to convey meaning to the other party. They are expressed by non-manual next to hand signs. Sign languages are natural languages that have their own vocabulary and grammatical structure. Although not universal, there are striking similarities between sign languages. Linguists consider communication through both speech and sign to be natural language, which means that both are the result of an abstract, prolonged process and a rigorous unplanned evolution over time. Sign languages should not be confused with body language, which is a non-verbal form of communication.