A Cardinal number represents an equivalence class of sets between which there is a bijection (one-to-one correspondence). It is the number of elements in any member of the equivalence class. An Ordinal number represents an equivalence class of well-ordered sets between which there is an order-preserving bijection. It is the number of elements in any member of the equivalence class. The difference is only in whether the sets are ordered.
It is the basis for protein manufacture in plants and plays a major part in photosynthesis. For lawns, shrubs and leafy houseplants, a nitrogen-rich fertilizer is the best choice. When reading a fertilizer package, nitrogen will be the first in a series of numbers appearing with dashes between them. For example, a formula of 10-0-0 is a nitrogen-only fertilizer.
If your soil is correctly balanced or high in nitrogen, you should use a fertilizer that is slightly lower in nitrogen and higher in phosphorus, such as a 5-10-5 or a 5-10-10 mixed fertilizer. If you are slightly lacking in nitrogen, use a balanced fertilizer like 8-8-8 or 10-10-10.