Prime-
(adj.)
1. First in excellence, quality, or value. See Usage Note at perfect.
2. First in degree or rank; chief. See Synonyms at chief.
3. First or early in time, order, or sequence; original.
Primal- (adj.)
1. Original, yet primitive
2. first in importance
Grade- (adj.)
1. a position of scale/ranks/equalities
2. something you don't want to receive from a teacher, but from your peers
3. being, involving, or yielding domestic animals of improved but not pure stock