The possibilities are almost limitless. Trademarks may be one or a combination of words, letters, and numerals. They may consist of drawings, symbols, three- dimensional signs such as the shape and packaging of goods, audible signs such as music or vocal sounds, fragrances, or colors used as distinguishing features.
In addition to trademarks identifying the commercial source of goods or services, several other categories of marks exist. Collective marks are owned by an association whose members use them to identify themselves with a level of quality and other requirements set by the association. Examples of such associations would be those representing accountants, engineers, or architects. Certification marks are given for compliance with defined standards, but are not confined to any membership. They may be granted to anyone who can certify that the products involved meet certain established standards. The internationally accepted "ISO 9000" quality standards are an example of such widely-recognized certifications.