In the European tradition, casual is the dress code that emphasizes comfort and personal expression over presentation, formality and conformity. This type of dress may be referred to as leisurewear. More simply, "casual" can be defined as something relaxed, occasional, not planned, or informal. It includes a very wide variety of costume, so it is perhaps better defined by what it is not than what it is. The following are not considered casual wear:
Business casual is an ambiguously defined dress code that has been adopted by many professional and white-collar workplaces in Western countries. It entails neat yet casual attire and is generally more casual than informal attire but more formal than casual or smart casual attire. Casual Fridays preceded widespread acceptance of business casual attire in many offices.
Smart casual is an ambiguously-defined dress code that is generally a neat yet casual attire. Different localities, kinds of events, contexts, or cultures can have varying interpretations of the dress code and therefore the designation of certain clothing pieces as smart casual is disputed.
Buying casual shirts online ?
Although it can be considered "informal" in the senses of "not formal" or "suited for everyday use," informal attire actually refers to a dress code much more formal than casual shirts, a step below semi-formal shirts.