What is the purpose of "me" in "Je me suis trompé dans mon calcul."?

Question

The sentence

Je me suis trompé dans mon calcul.

can be translated as

I've made a mistake in my calculation.

However, I don't understand the purpose of "me" in that sentence; for example,

je -> I

suis trompé -> have made

dans -> in

mon calcul -> my calculation

so if we didn't put "me" there, would the meaning change ?

Answer 1

You confusion is due to the fact the most idiomatic ways to express it differs between French and English. However there are alternative forms with a closer structure in both cases.

I've made a mistake in my calculation.

word by word translates to:

J'ai fait une erreur dans mon calcul.

while

Je me suis trompé dans mon calcul.

literally translates to:

I mislead myself in my computation.

Answer 2

This particular verb in French that means "to make an error", "to err", is a pronominal verb; it's just like that; you can use other verbs, but they are not heard so often and they are verbal locutions instead of simple one word terms: "commettre une erreur", "faire une erreur". In a pronominal verb, just as in English, you have to use the pronoun all the time; there is no way to omit it. This pronoun, moreover, has nothing to do with the possessive adjective "mon"; that word is in the noun group not the verb group: you can replace it by all of these words in turn and say something a little different each time without changing the verb;

ce, le, un, leur, ses, mes, tous ces, certains, etc. ("calcul" or "calculs" according to gender)

The conjugation is as follows ;

je me suis trompé
tu t'es trompé
il s'est trompé
nous nous sommes trompés
vous vous êtes trompés
ils se sont trompés

Answer 3

It's often not a good idea to translate word for word. You made a mistake when you said "suit trompe -> have made".

You should have included "a mistake", but also "me".

me suis trompé -> have made a mistake

In French, to make a mistake is se tromper. As Jlliagre said, it's reflexive because literally it means "to mislead oneself".

(It's a little more subtle than that, you should go see all the meanings of "tromper" and "se tromper".)