Tromper vs. se tromper
The French verbs tromper and se tromper are often confusing for learners because they look similar but have very different meanings. The key difference lies in the reflexive pronoun se, which completely changes the meaning from an action done to someone else to an action done to oneself, like making a mistake.
Tromper
B1This is a transitive verb that means to deceive, to mislead, to fool, or to cheat on someone. The action is directed towards another person or group.
Le vendeur a essayé de me tromper sur le prix.
(The salesman tried to deceive me about the price.)
Il a trompé sa femme pendant des années.
(He cheated on his wife for years.)
Les apparences peuvent souvent tromper.
(Appearances can often be deceiving.)
Ne te laisse pas tromper par ses belles paroles.
(Don't let yourself be fooled by his nice words.)
Cette carte est conçue pour tromper l'ennemi.
(This map is designed to mislead the enemy.)
Se tromper
A2This is a reflexive verb that means to be mistaken, to make a mistake, or to be wrong. The action reflects back on the subject. It is about an error, not deception.
Excusez-moi, je me suis trompé de numéro de téléphone.
(Excuse me, I have the wrong phone number.)
Si je ne me trompe pas, le magasin ferme à 18h.
(If I'm not mistaken, the store closes at 6 pm.)
Elle s'est trompée de chemin et elle est arrivée en retard.
(She took the wrong road and she arrived late.)
Tu te trompes complètement sur son caractère.
(You are completely mistaken about his character.)
Nous nous sommes trompés dans nos calculs.
(We made a mistake in our calculations.)
Summary
In essence, tromper is an action you do to someone else: you deceive them. Se tromper is an action you do to yourself: you make a mistake. The first is about dishonesty towards others, while the second is about being incorrect yourself.