Future and conditional: stems, endings and uses

For -er and -ir verbs, the stem is generally the full infinitive; -re verbs drop final e: prendre gives je prendrai. For the future you add the endings of “avoir” — “-ai, -as, -a, -ons, -ez, -ont” — giving “je partirai, tu partiras, il partira”. For the conditional you add those of the imparfait — “-ais, -ais, -ait, -ions, -iez, -aient” — giving “je partirais”.

Notice what that means: learn one stem and you have two tenses. And the other way round, if a stem is irregular it is irregular in both: “aller” gives “j'irai” and “j'irais”; “avoir” gives “j'aurai” and “j'aurais”; “être”, “je serai” and “je serais”. There are about a dozen and they have to be learnt.

In speech, though, the future you hear is a different one: “aller” in the present plus an infinitive. “Je vais partir”, “on va voir”. It is not less correct nor inherently more casual; it is especially frequent for near or already-arranged plans.

And there is a French rule that will cost you, because English does the opposite: after “quand”, “lorsque” and “dès que”, when you are talking about the future, French uses the future. “Quand j'arriverai, je t'appellerai”. English says “when I arrive”; French marks the future in both halves of the sentence.

The conditional, besides saying what someone would do, is how you ask for something without ordering it. “Je voudrais un café” is the ordinary way to order; “je veux un café” is perfectly understandable and sounds like a demand.