1. The reproductive organ in female animals in which eggs (ova) are produced. In most vertebrates there are two ovaries (in some fish the ovaries fuse together to form a single structure and in birds the left ovary only is functional). As well as eggs, they produce steroid hormones (see oestrogen; progesterone). In mammals each ovary is situated close to the opening of a fallopian tube; it contains numerous follicles in which the eggs develop and from which they are released in a regular cycle. See also graafian follicle; menstrual cycle; oogenesis; ovarian cycle; ovulation; reproductive system.

2. The hollow base of the carpel of a flower, containing one or more ovules. After fertilization, the ovary wall develops into the fruit enclosing the seeds. In some species, the carpels are fused together to form a complex ovary.