Clothing is an aspect of human physical appearance, an like other aspects of human physical appearance it has social significance. All societies have dress codes, most of which are unwritten but understood by most members of the society. The dress code has built in rules or signals indicating the message being given by a person's clothing and how it is worn. This message may include indications of the person's social class, income, occupation, ethnic and religious affiliation, attitude, marital status, sexual availability and sexual orientation. Clothes convey other social messages including the stating or claiming personal or cultural identity, the establishing, maintaining, or defying social group norms, and appreciating comfort and functionality.