limb vs arm

limb and arm both are nouns.

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

As nouns, limb and arm are synonyms defined as:

Other synonyms of limb include branch.

As nouns, arm is a hyponym of limb; that is, arm is a word with a more specific, narrower meaning than limb:

limb: one of the jointed appendages of an animal used for locomotion or grasping: arm, leg, wing, flipper
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

Other hyponyms of limb include hind limb, hindlimb, forelimb, flipper, leg, crus, leg, thigh, cubitus, forearm.

limb (noun)	arm (noun)
any projection that is thought to resemble a human arm	the part of a garment that is attached at the armhole and that provides a cloth covering for the arm
the graduated arc that is attached to an instrument for measuring angles	any instrument or instrumentality used in fighting or hunting
either of the two halves of a bow from handle to tip	the part of an armchair or sofa that supports the elbow and forearm of a seated person
one of the jointed appendages of an animal used for locomotion or grasping: arm, leg, wing, flipper	any projection that is thought to resemble a human arm
(astronomy) the circumferential edge of the apparent disc of the sun or the moon or a planet	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
any of the main branches arising from the trunk or a bough of a tree	a division of some larger or more complex organization

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