mesial

As an adjective mesial

is pertaining to the middle line of the body.

As a noun hemisection is

a division along the mesial plane.

In dentistry|lang=en terms the difference between mesial and mesiolingual

is that mesial is (dentistry) facing the side of a tooth which faces the middle of the jaw while mesiolingual is (dentistry) of, pertaining to or connecting the mesial and lingual surfaces of a tooth.

As adjectives the difference between mesial and mesiolingual

is that mesial is pertaining to the middle line of the body while mesiolingual is (dentistry) of, pertaining to or connecting the mesial and lingual surfaces of a tooth.