sleeping pill vs sleeping capsule

sleeping pill and sleeping capsule both are nouns.

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

As nouns, sleeping pill and sleeping capsule are synonyms defined as:

sleeping pill and sleeping capsule: a soporific drug in the form of a pill (or tablet or capsule)

Other synonyms of sleeping pill include sleeping draught, sleeping tablet.

sleeping pill (noun)	sleeping capsule (noun)
a soporific drug in the form of a pill (or tablet or capsule)	a soporific drug in the form of a pill (or tablet or capsule)