tablet vs capsule

tablet and capsule both are nouns.

Word	Noun	Adjective	Verb	Adverb
tablet	Yes	No	No	No
capsule	Yes	No	Yes	No

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

tablet: a dose of medicine in the form of a small pellet
capsule: a pill in the form of a small rounded gelatinous container with medicine inside

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

tablet (noun)	capsule (noun)
a dose of medicine in the form of a small pellet	a pill in the form of a small rounded gelatinous container with medicine inside
a small flat compressed cake of some substance	a spacecraft designed to transport people and support human life in outer space
a slab of stone or wood suitable for bearing an inscription	a small container
a portable computer with a touchscreen	a pilot's seat in an airplane that can be forcibly ejected in the case of an emergency; then the pilot descends by parachute
a number of sheets of paper fastened together along one edge	a structure that encloses a body part
	a shortened version of a written work
	a dry dehiscent seed vessel or the spore-containing structure of e.g. mosses

tablet (verb)	capsule (verb)
	put in a short or concise form; reduce in volume
	enclose in a capsule