A particle is a small word that does not change its form and has a grammatical function in a sentence.
Sentences
In English, particles like 'up' and 'out' can change the meaning of a verb.
She turned down the offer.
Japanese: 彼女はよく本を読みます。(She often reads books.)
Spanish: Él llegó tarde a la fiesta. (He arrived late to the party.)
French: Il a déjà mangé. (He has already eaten.)