The scientific classification of Cotyledon and Cereus includes the entire classification chart that includes kingdom, family, clade, tribe etc. A kingdom is the second highest taxonomic rank. A taxonomic rank is the level that a living organisms are placed in hierarchical level of arrangement of life forms. All the living organisms are divided into kingdoms. Plant kingdom is a main classification of living organisms that include all plants. There are six kingdoms which are: Plantae, Animalia, Fungi, Protista, Aschaea/Archaeabacteria and Bacteria Eubacteria. Cotyledon and Cereus kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Cotyledon and Cereus family is a major factor of Cotyledon and Cereus Scientific Classification. Plant family helps you narrow the search of your plants. It also gives you idea about, how the plant looks, how the seed will be like etc. These two plant families can be different or same. Cotyledon belongs to the family Crassulaceae and Cereus belongs to the family Cactaceae.
While comparing scientific classification, Cotyledon and Cereus genus and other classification are also important. Also, when you compare Cotyledon and Cereus, other factors should also be taken into considerations like order, subfamilies, tribe, clade etc. First plant's genus is Cotyledon L. and other plant's genus is Selenicereus. Cotyledon tribe is Not Available and Cereus tribe is Hylocereeae. Cotyledon clade is Rosids and order is Rosales whereas Cereus clade is Angiosperms, Core eudicots and Eudicots and order is Caryophyllales. Every plant have subfamilies. Cotyledon subfamilies are, Not Available and Cereus subfamilies are Cactoideae. In this way you can compare scientific classification of Cotyledon and Cereus and other products also.