(Alternate spelling: fertilisation).
1. Creation by the union of sperm or pollen with an animal or plant or egg cell; SYN. fertilisation, fecundation, impregnation.
2. Making fertile as by applying fertilizer or manure; SYN. fecundation, dressing.
In sexual reproduction, the union of two gametes (sex cells, often called egg and sperm) to produce a zygote, which combines the genetic material contributed by each parent. In self-fertilization the male and female gametes come from the same plant; in cross-fertilization they come from different plants. Self-fertilization rarely occurs in animals; usually even hermaphrodite animals cross-fertilize each other.
In terrestrial insects, mammals, reptiles, and birds, fertilization occurs within the female's body. In humans it usually takes place in the Fallopian tube. In the majority of fishes and amphibians, and most aquatic invertebrates, fertilization occurs externally, when both sexes release their gametes into the water. In most fungi, gametes are not released, but the hyphae of the two parents grow toward each other and fuse to achieve fertilization. In higher plants, pollination precedes fertilization.