Is in an environment a prepositional phrase?

It depends! "In an environment" can be a prepositional phrase, but it can also be a noun phrase.

Prepositional Phrase:

* Structure: It has a preposition ("in") followed by a noun phrase ("an environment").

* Example: "The plants thrive in an environment with plenty of sunlight."

Noun Phrase:

* Structure: It acts as a noun, referring to a specific location.

* Example: "Living in an environment with constant noise can be stressful."

To determine its function, you need to look at the surrounding context.