germ

The embryo of a seed, especially of a seed used as a cereal or grain. See Wikipedia article on cereal germ.

(biology) The small mass of cells from which a part of an organism develops, or a macroscopic but immature form of that part; a bud.

A pathogen: a pathogenic microorganism, such as a bacterium or virus.

(figuratively) The origin or earliest version of an idea or project.

(mathematics) An equivalence class that includes a specified function defined in an open neighborhood.