Noun: This is the most common usage. It refers to work, especially physical work.
* Examples: "The factory workers protested for better labor conditions."
* "The company is experiencing a shortage of labor."
Verb: This usage means to work hard, often physically.
* Examples: "They labored for hours to build the house."
* "The farmers labored in the fields from dawn to dusk."
Adjective: This is a less common usage, meaning relating to work or workers.
* Examples: "The labor movement has fought for worker's rights."
* "The labor union negotiated a new contract with the company."
So, to determine the part of speech, you need to consider its context in the sentence.