Uniforms are special clothes to show that a group of people belong together. The group of people will all be dressed in the same way ("uni" means "one", and form means "shape" one shape).
People may wear uniforms for several reasons. The uniform will help the people to feel a team spirit so that they work well together. They may also help members of the public to know who they are, e.g. in a department store a customer can tell who is a member of staff, or in the street people will recognize a police officer. Uniforms may also be worn because they are practical, e.g. it might keep them safe when operating machinery or keep them clean when doing their work.
Nurses in hospitals wear uniforms. Sometimes domestic workers wear uniforms when working for their employers. Important domestic workers may wear special smart uniforms called "livery" e.g. porters (doormen) at luxury hotels.
In some countries such as India, Japan, China, Korea, Australia and the United Kingdom, many school children wear uniforms. These uniform would usually be a set of clothes with the school crest or symbol. It helps them to feel proud of their school and children from rich families and poor families all look the same. In Britain, for example, most young children wear school uniforms. In state schools. the children may wear polo-necked T shirts with a school logo. Other schools, especially private schools, may have a formal uniform, or they may be free to choose their own clothes so long as they are the school color.