arm vs cubitus

arm and cubitus both are nouns.

Word	Noun	Adjective	Verb	Adverb
arm	Yes	No	Yes	No
cubitus	Yes	No	No	No

arm (noun)	cubitus (noun)
the part of a garment that is attached at the armhole and that provides a cloth covering for the arm	hinge joint between the forearm and upper arm and the corresponding joint in the forelimb of a quadruped
any instrument or instrumentality used in fighting or hunting	the arm from the elbow to the fingertips
the part of an armchair or sofa that supports the elbow and forearm of a seated person
any projection that is thought to resemble a human arm
a human limb; technically the part of the superior limb between the shoulder and the elbow but commonly used to refer to the whole superior limb
a division of some larger or more complex organization

arm (verb)	cubitus (verb)
prepare oneself for a military confrontation
supply with arms