The scientific classification of Onion and Celery 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. Onion and Celery kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Onion and Celery family is a major factor of Onion and Celery 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. Onion belongs to the family Liliaceae and Celery belongs to the family Apiaceae.
While comparing scientific classification, Onion and Celery genus and other classification are also important. Also, when you compare Onion and Celery, other factors should also be taken into considerations like order, subfamilies, tribe, clade etc. First plant's genus is Allium and other plant's genus is Apium. Onion tribe is Allieae and Celery tribe is Apieae. Onion clade is Angiosperms and Monocots and order is Asparagales whereas Celery clade is Angiosperms, Asterids and Eudicots and order is Apiales. Every plant have subfamilies. Onion subfamilies are, Allioideae and Celery subfamilies are Apioideae. In this way you can compare scientific classification of Onion and Celery and other products also.