What term describes the joining of egg and sperm cells?

The joining of egg and sperm cells is specifically termed fertilization. This process is crucial for sexual reproduction, as it marks the beginning of embryonic development. During fertilization, the genetic material from both the egg and sperm combine to form a zygote, which will then undergo multiple divisions and developments to eventually form a new organism.

In contrast, germination refers to the process by which a seed develops into a new plant, pollination involves the transfer of pollen from one flower to another to enable fertilization in plants, and fusion is a more general term that can refer to the combination of any elements, but it is not commonly used to describe the specific biological process of egg and sperm merging. Thus, fertilization is the most precise term for the joining of egg and sperm cells.