tab vs sleeping pill

tab and sleeping pill both are nouns.

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

As nouns, sleeping pill is a hyponym of tab; that is, sleeping pill is a word with a more specific, narrower meaning than tab:

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

Other hyponyms of tab include bolus, capsule, dragee, sleeping capsule, sleeping draught, sleeping tablet.

tab (noun)	sleeping pill (noun)
a dose of medicine in the form of a small pellet	a soporific drug in the form of a pill (or tablet or capsule)
a short strip of material attached to or projecting from something in order to facilitate opening or identifying or handling it
the key on a typewriter or a word processor that causes a tabulation
the bill in a restaurant
sensationalist journalism