tremor vs trembling

tremor and trembling both are nouns.

Word	Noun	Adjective	Verb	Adverb
tremor	Yes	No	Yes	No
trembling	Yes	Yes	No	No

As nouns, trembling is a hypernym of tremor; that is, trembling is a word with a broader meaning than tremor:

tremor: shaking or trembling (usually resulting from weakness or stress or disease)
trembling: a shaky motion

Other hypernyms of tremor include palpitation, quiver, quivering, shakiness, shaking, vibration.

tremor (noun)	trembling (noun)
an involuntary vibration (as if from illness or fear)	a shaky motion
a small earthquake
shaking or trembling (usually resulting from weakness or stress or disease)

tremor (adjective)	trembling (adjective)
	vibrating slightly and irregularly; as e.g. with fear or cold or like the leaves of an aspen in a breeze

tremor (verb)	trembling (verb)
shake with seismic vibrations