The word "歹徒" is formed as a compound noun through the combination of two characters: "歹", which means "bad", "evil", or "wicked", and "徒", which means "follower", "person", or "disciple". Together, they create a modifier-noun structure where "歹" acts as an adjective describing the type of "徒", resulting in the meaning "a follower of evil" or "an evil person", and by extension, a common term for a "criminal", "gangster", or "villain". This formation follows a typical pattern in Chinese where two meaningful characters are combined to produce a new, specific concept.