The scientific classification of Allamanda 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. Allamanda and Cereus kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Allamanda and Cereus family is a major factor of Allamanda 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. Allamanda belongs to the family Apocynaceae and Cereus belongs to the family Cactaceae.
While comparing scientific classification, Allamanda and Cereus genus and other classification are also important. Also, when you compare Allamanda and Cereus, other factors should also be taken into considerations like order, subfamilies, tribe, clade etc. First plant's genus is Allamanda and other plant's genus is Selenicereus. Allamanda tribe is Apocyneae and Cereus tribe is Hylocereeae. Allamanda clade is Angiosperms, Asterids and Eudicots and order is Gentianales whereas Cereus clade is Angiosperms, Core eudicots and Eudicots and order is Caryophyllales. Every plant have subfamilies. Allamanda subfamilies are, Rauvolfioideae and Cereus subfamilies are Cactoideae. In this way you can compare scientific classification of Allamanda and Cereus and other products also.