Basal is a term with several scientific meanings:

• A basal clade is one which forms an outgroup to a larger clade. As such the term is relative.
• Basal (medicine) refers to a type of insulin dosing.
• The basal ganglia are a region of the brain.
• The basal lamina is the surface on which epithelial cells are attached.
• An anatomical term of location, for features associated with the base of an organism or structure, such as the end of a sponge that adheres to its substrate.

other meanings:

• Basal, a village in Hungary