To answer succinctly: these words are all separate parts of speech and are used differently in sentences.
- were is the past tense plural form of “to be.” It describes actions or states that involved more than one subject in the past (or in conditional/ subjunctive mood). Example: They were happy yesterday. If I were there, I could help.
- in is a preposition or adverb indicating location or position. It shows where something is or when something happens as part of phrases like in the room, in 2020.
- a is an indefinite article used before a singular count noun to refer to one unspecified item. Example: a sentence.
- sentence is a noun meaning a set of words that expresses a complete thought, or a sentence can be a grammatical construct with a subject and predicate. Example: The sentence was long.
If you’d like, provide a specific sentence and I’ll break down how each element functions in that context.
