sink vs sink in

sink is a noun but sink in is not a noun.

Word	Noun	Adjective	Verb	Adverb
sink	Yes	No	Yes	No
sink in	No	No	Yes	No

sink (noun)	sink in (noun)
plumbing fixture consisting of a water basin fixed to a wall or floor and having a drainpipe
a covered cistern; waste water and sewage flow into it
a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof
(technology) a process that acts to absorb or remove energy or a substance from a system

sink (verb)	sink in (verb)
fall heavily or suddenly; decline markedly	become clear or enter one's consciousness or emotions
embed deeply	pass through
go under
fall or descend to a lower place or level
cause to sink
fall or sink heavily
appear to move downward
descend into or as if into some soft substance or place
pass into a specified state or condition; sink into