tab vs sleeping capsule

tab and sleeping capsule both are nouns.

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

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

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

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

tab (noun)	sleeping capsule (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