A notion is a general concept, theory, or impression. However, in American English, the word often implies a mistaken, foolish, or silly idea. People describe an idea as a notion to indicate that they don’t agree with the idea or the thinking that led to it.
“Your neighbor has some strange notions.”
“I don’t know where the clerk got that notion.”
In other words, “notion” has a negative connotation that might distract your readers. Instead, use words like idea, concept, conclusion, theory, or hypothesis.
Connotation: an idea that is associated with or implied by a word, though not explicitly part of its definition.