* Common Noun: A common noun refers to a general person, place, or thing. "Trouble" is a general concept that can be applied to many situations.
* Compound Noun: A compound noun is formed by combining two or more words. "Trouble" is a single word, so it's not a compound noun.
* Abstract Noun: An abstract noun refers to an idea, concept, quality, or state of being. "Trouble" fits this definition as it represents a state of difficulty or distress.
* Collective Noun: A collective noun represents a group of people or things. "Trouble" doesn't represent a group.
* Proper Noun: A proper noun refers to a specific person, place, or thing (usually capitalized). "Trouble" is not a specific thing.
In summary: "Trouble" is a common noun because it refers to a general concept and is not a specific person, place, or thing.