Sign language (also known as signed language) is a language that uses manual communication to convey meaning. This can include simultaneously employing hand gestures, movement, orientation of the fingers, arms or body, and facial expressions to convey a speaker's ideas. Sign languages often share significant similarities with their respective spoken language (such as ASL and American English). Grammar and sentence structure, however, may vary to encourage efficiency and fluidity in speaking. It is important to note that just because a spoken language is intelligible transnationally (e.g. The United States and The United Kingdom, which both use forms of English), does not mean that the sign languages from those regions are as well. For example, ASL and BSL were formed independently and are therefore unintelligible. Linguists consider both spoken and signed communication to be types of natural language, meaning that both emerged through an abstract, protracted aging process and evolved over time without meticulous planning. Sign language should not be confused with "body language", a type of nonverbal communication.