Lactogenesis. The  production of milk.

Lactose. (milk sugar). A sugar comprising one glucose molecule linked to a galactose molecule is manufactures by the mammary gland and occurs only in milk. For example, cows, milk contains about 47% lactose. It is less sweet than sucrose (cane sugar)

Lactose synthetase. An enzyme that catalyses the synthesis of Lactose from glucose.

Lacuna.  A gap or cavity in the tissue of an organism; for example, the hollow centre of certain plant stems or any of the small cavities in bone in which the bone-forming cells are found.

Lacunate. Divided into narrow segments in deep and irregular manner.

Leteral plate.  The mesoderm in the ventrolateral position in the vertebrate embryo.

Latiseptate. Having a septum across the widest diameter, as on some fruits.

Leaching. The process by which nutrient are removed from the soil by the percolation of water through it.

Lectin. protein with combining groups that reacts, much as an antibody does, with specific carbohydrate components of other molecules. Widely used for specific making of cells. Commonly obtained from plants.

Lectotype. Specimen selected from the original material to serve as the type specimen when this was not designated at the time of publication or is missing.

Leech. An aquatic annelid of the order Hirudinea.