For as long as humans have lived on the earth, they have made use of various forms of communication. Generally, this expression of thoughts and feelings has been in the form of oral speech. When there is a spoken language problem, communication can be carried out through sign language, in which gestures stand for letters, words, and ideas. Tourists and people unable to hear or speak have often had to turn to this form of expression. When gestures describe words or ideas, they can often be used internationally. When used for spelling words however, where each gesture stands for a single letter, people must share the same written language. Body language sends ideas or thoughts by certain actions, either meaningfully or not. A wink can be a way of showing that the person is only joking. A nod means agreement, while shaking the head indicates disagreement. Other forms of language can be found in Braille (a reading system of raised dots read with the fingertips used by the blind), signal flags, Morse code, and smoke signals. Road maps and picture signs also guide and warn people. While language is the most common form of communication, other systems and techniques also express human thoughts and feelings. What does the author mainly want to say?
People can communicate in many different ways. Everybody uses only one form of communication. Language is invaluable to foreigners. Non-spoken communication is of little value.