A dress code is a set of rules governing what garments may be worn together and in what setting. In Western culture, examples of dress codes are combinations such as "smart casual", or "morning dress". A classification of these codes is normally made for varying levels of formality and times of day. In traditional Western dressing, for men the more formal dress codes, such as "black tie", are highly codified with essentially fixed definitions, mostly unchanged for more than fifty years, while the more casual classifications change very quickly, and a worldwide or widely relevant discussion is impossible. For women, changes in fashion are more rapid.
In practical use, dress codes are either followed intuitively or enforced by peer pressure, so that people wear similar clothing in the same situations. Alternatively, at more formal events where a dress code is specified, invitees wear clothes at the specified level; if some variation is permitted (for example, "black tie preferred"), the host will wear the most formal option to save guests the embarrassment of out-dressing him. Appropriate national dress is generally permitted, and national variations are also widely worn as an exception to the trend of uniformity with peers, often in the form of headgear (see kippa, turban, hijab).