plant vs pot plant

plant and pot plant both are nouns.

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

plant (noun)	pot plant (noun)
buildings for carrying on industrial labor	a plant suitable for growing in a flowerpot (especially indoors)
(botany) a living organism lacking the power of locomotion
an actor situated in the audience whose acting is rehearsed but seems spontaneous to the audience
something planted secretly for discovery by another

plant (verb)	pot plant (verb)
put or set (seeds, seedlings, or plants) into the ground
fix or set securely or deeply
set up or lay the groundwork for
place into a river
place something or someone in a certain position in order to secretly observe or deceive
put firmly in the mind