* Verb: This is the most common usage, meaning to damage or spoil something. For example, "The storm marred the beautiful garden."
* Noun: In some contexts, "mar" can be a noun referring to a husband (archaic). For example, "She was a loyal wife to her mar."
* Proper noun: "Mar" can also be a proper noun, like a person's name.
To determine the correct part of speech, you need to look at the sentence it's used in.