Sperm cells are male reproductive cells that are responsible for fertilizing female eggs. They are commonly referred to as "spermatozoa", "spermatozoon", "gametes", or "seed". In the animal kingdom, sperm cells are often referred to as "spermatozoa" or "sperm", while in the plant kingdom, they are called "pollen". In scientific literature, the word "sperm" is often used interchangeably with "sperm cell", while other synonyms for sperm cells include "spermatozoan", "sperm cell", "spermatozoid", and "male gamete". While the term "sperm" is the most commonly used, the other synonyms for sperm cells can also be employed in order to provide a diversified vocabulary in academic writing.