The word ‘problem’ is primarily used as a noun.
Nouns are words that name people, places, things, or ideas. In this case, ‘problem’ refers to a matter or situation regarded as unwelcome or harmful and needing to be dealt with and overcome. For example, in the sentence ‘The problem needs to be solved,’ the word describes a specific issue or challenge.
In some contexts, ‘problem’ can also be used in a more specialized manner, such as in mathematics, where it refers to a question or exercise that tests a person’s understanding of a concept. However, regardless of the context, ‘problem’ functions as a noun in English grammar.