An ovary has only one ovule, and an ovule can only develop into a seed.

An ovary can have multiple ovules, and a complete seed includes embryo, endosperm or cotyledon and seed coat. Seeds are developed from fertilized ovules, that is, an egg, two polar nuclei and two sperm in the ovule are formed by double fertilization.

The fruit develops from the ovary, the ovary wall develops into the fruit skin, and the ovule is located in the ovary. Many plants have more than one ovule in the ovary, but some plants have only one ovule in the ovary, so there is only one seed in the fruit.