to warn you; to let you know
I came to warn you.
I just wanted to let you know.
Je suis venu te prévenir, père.
I came to warn you, Father.
— Oncle Boonmee (celui qui se souvient de ses vies antérieures) (2010)
I have to warn you.
I wanted to warn you.
Alors j'ai pensé que c'était plus gentil de venir te prévenir.
So I thought it would be kinder to come and let you know.
— Monsieur Hire (1989)
Pouvais-je passer sans te prévenir ?
Could I just drop by without letting you know?
— Cléo from 5 to 7 (1962)
I should have warned you.
J'aurais dû te prévenir plus tôt.
I should have warned you earlier.