Genus Carduus refers to a group of thistle plants that belong to the family Asteraceae. This genus comprises numerous species, including the common thistle, Scotch thistle, and milk thistle. There are several synonyms for this genus, including Cirsium, Onopordum, and Silybum. Cirsium contains several thistle species that are closely related to Carduus and are often referred to as "plume thistles." Onopordum usually refers to the tall, spiky thistles that are commonly found in Mediterranean regions. Silybum includes the milk thistle species that have medicinal properties. Although these botanical names have different applications, they are often used interchangeably, making it important to identify the specific species within the genus Carduus.