* Noun: When referring to a large amount or quantity of something, or a body of matter.
* Example: "There was a large mass of people gathered in the square."
* Example: "The mass of the Earth is approximately 5.972 × 10^24 kg."
* Adjective: When describing something as being large or weighty, or referring to a special religious service.
* Example: "The mass production of cars has changed the world."
* Example: "We attended mass at the cathedral."
* Verb: When referring to the act of gathering together, or to accumulate.
* Example: "The protestors massed in front of the government building."
The specific part of speech depends on how the word is used in a sentence.