* All words have a grammatical function. While some words are primarily used as nouns (like "table" or "cat"), others are primarily used as verbs (like "run" or "eat"), adjectives (like "big" or "happy"), adverbs (like "quickly" or "loudly"), prepositions (like "on" or "under"), conjunctions (like "and" or "but"), and so on.
* Words can change function. A word like "run" can be a verb ("I run every day") or a noun ("The run was tiring").
So, to answer your question directly, there isn't a word that is *not* a noun. Every word has a grammatical function.
Do you have any other questions about grammar or words? 😊