Basal

From Freepedia

In phylogenetics, basal members of a group are subgroups that diverged very early from the others. For instance, palaeodicots are basal flowers, diverging before the main split between the monocots and eudicots. Orangutans are the most basal of the great apes, having diverged from the line earliest. The term is used contextually, rather than describing any precise group.

The term is also used by diabetics and health care professionals to describe a low, continuous dosage of insulin (either from an insulin pump or a slow-acting injection) intended to "cover" the glucose output of the liver. This is as opposed to a bolus, which is a dosage of insulin intended to "cover" a meal.