* Noun: This is the most common usage, referring to a line that marks the limits of something. For example, "We need to set clear boundaries for the children's playtime."
* Verb: "Boundaries" can be used as a verb, meaning to limit or restrict something. For example, "The company boundaries its marketing efforts to specific demographics."
* Adjective: While less common, "boundaries" can also act as an adjective. For example, "The boundaries region is known for its beautiful scenery."
To understand the part of speech, you'll need to look at the context of the sentence.