Fetching details from the dictionary...

particle; postpositional word in Japanese grammar that functions as an auxiliary to a main word
日本語の助詞の使い方は外国人には難しい。
Japanese particles are difficult for foreigners.
日本語の助詞は難しいですね。
Japanese particles are difficult, aren't they?
助詞を間違えると意味が変わってしまう。
Using the wrong particle changes the meaning.