arachnid

This term is a scientific classification that encompasses a wide variety of creatures beyond just spiders. It carries a clinical, biological tone and is typically used in academic or natural history contexts to group animals by their shared anatomical traits, such as the absence of antennae. As a countable noun, it follows standard English pluralization rules. While the word refers to a broad class of animals, it is used as a common noun when referring to an individual specimen or the group in general.