What is the taxonomic classification for a crab?

Hint: Taxonomy (that apparently means "arrangement law") is the study of characterizing organisms in order to create globally categorization systems that group every organism into greater encompassing sections. A hierarchical system is one that organizes things from considerably larger to smaller, more precise groups

Complete answer:
Scientists organize organisms into three big groupings termed domains after the fundamental origin of all life: Bacteria, Archaea, and Eukarya. Under every domain, there is a subsection known as a kingdom. The following groups of increasing specialization after kingdoms are phylum, class, order, family, genus, and species. Within scientific categorization, groups are organized in order of ascending intricacy.
The seven levels of classification for a crab are as follows:
Kingdom: Animalia (One of the most distinguishing features of this kingdom is the lack of a cell wall)
Phylum: Arthropoda (Arthropods are characterized by their fused exoskeleton covering, which is made up of chitin linked to protein)
Subphylum: Crustacea (All crustaceans undergo a larval stage called nauplius, which is one of their commonalities)
Class: Malacostraca (Body is distinct)
Order: Decapoda (The word decapod comes from the occurrence of five pairs of thoracic legs)
Genus: Carcinus
Species: maenas

Note:
Crab occupy a domain (Eukarya) with organisms with the greatest genetic variation, including plants and butterflies. The animals are more likely to be related at each sublevel, therefore they appear more comparable. Scientists used to classify animals based on their morphological traits, but as DNA technology advanced, more accurate phylogenetic analysis based on genetic resemblance were discovered