(usu in pl) a basic principle or element, or a fundamental skill
(usu in pl) something as yet unformed or undeveloped
the rudiments of a plan
a deficiently developed body part or organ; = vestige (2)
a body part or organ in its earliest stage of development or when just beginning to develop; = primordium
rudimental /-ʹmentl/ adj
[Latin rudimentum beginning, from rudis raw, rude]