What part of speech is gas?

"Gas" can be a few different parts of speech depending on its usage:

* Noun: When referring to the physical state of matter, it's a noun. For example: "The gas in the balloon is helium."

* Verb: It can be a verb meaning to supply with fuel or to fill with gas. For example: "We need to gas up the car."

* Informal adjective: It can be used informally as an adjective meaning "full of gas" or "very energetic." For example: "He was full of gas after drinking the energy drink."

Therefore, the part of speech of "gas" depends on its context.