sleeping pill vs tablet

sleeping pill and tablet both are nouns.

Word	Noun	Adjective	Verb	Adverb
sleeping pill	Yes	No	No	No
tablet	Yes	No	No	No

As nouns, tablet is a hypernym of sleeping pill; that is, tablet is a word with a broader meaning than sleeping pill:

sleeping pill: a soporific drug in the form of a pill (or tablet or capsule)
tablet: a dose of medicine in the form of a small pellet

Other hypernyms of sleeping pill include lozenge, pill, tab, hypnotic, soporific.

sleeping pill (noun)	tablet (noun)
a soporific drug in the form of a pill (or tablet or capsule)	a dose of medicine in the form of a small pellet
	a small flat compressed cake of some substance
	a slab of stone or wood suitable for bearing an inscription
	a portable computer with a touchscreen
	a number of sheets of paper fastened together along one edge