Basic, elementary; relating to, or forming, the base, or point of origin.
In a phylogenetic tree, being a group, or member of a group, which diverged earlier. The earliest clade to branch in a larger clade.
Associated with the base of an organism or structure.
Of a minimal level that is necessary for maintaining the health or life of an organism.
base, bottom, minimum
Any basal structure or part
Of or pertaining to formation (in any of many contexts).