Le délai est plus court que prévu, donc nous devons répondre aujourd’hui.

Délai usually means a time limit, allowed period, or deadline window for doing something.

• le délai = the time allowed / the time frame
• le temps = time in a general sense
• la date limite = the final due date

So Le délai est plus court suggests that the amount of time available is shorter than expected, not just that time in general is short.

In French, court is the normal adjective for something that lasts a short time or covers a short duration.

So you say:

• un délai court = a short deadline / short time frame
• une courte pause = a short break

Petit usually means small in size or sometimes young, so it would sound unnatural here.

This is the standard French comparison pattern:

• plus + adjective + que = more ... / -er ... than

So:

• plus court que prévu = shorter than expected

Other examples:

• plus grand que = taller/bigger than
• plus rapide que = faster than
• plus difficile que = more difficult than

Because in comparisons, French uses que where English uses than.

Examples:

• plus grand que moi = taller than me
• moins cher que ça = cheaper than that
• aussi important que = as important as

So in this sentence, que is not that or what. It is the comparison word than.

Prévu is the past participle of prévoir, which means to foresee, to expect, or to plan.

So que prévu means something like:

• than expected
• than planned
• than was anticipated

In natural English, plus court que prévu is often translated as shorter than expected.

French often shortens this kind of expression. Que prévu is an elliptical structure, meaning that part of the sentence is left understood.

It can imply something like:

• que ce qui était prévu
• que nous l’avions prévu
• qu’on avait prévu

But French normally prefers the shorter version here:

• plus court que prévu
• plus long que prévu
• plus difficile que prévu

This is very common and natural.

The comma helps separate the two ideas:

1. Le délai est plus court que prévu
2. donc nous devons répondre aujourd’hui

Donc means so, therefore, or thus, and it often introduces a conclusion or consequence.

The comma is very natural in writing because the second part follows logically from the first: the deadline is shorter, so we must respond today.

Here donc means so or therefore.

It connects cause and result:

• Le délai est plus court que prévu → the available time is shorter than expected
• donc nous devons répondre aujourd’hui → so we have to reply today

It is a very common connector in French for logical conclusions.

Because devoir is a modal verb, like must, have to, or should in English.

With modal verbs, French typically uses:

• conjugated modal verb + infinitive

So:

• nous devons répondre = we must reply
• je peux venir = I can come
• ils veulent partir = they want to leave

Only devons is conjugated here. Répondre stays in the infinitive.

Both are possible, but nous is more explicit and often a bit more formal or written.

• nous devons répondre aujourd’hui = we must reply today
• on doit répondre aujourd’hui = we have to reply today

In everyday spoken French, on is very common for we. In more neutral or formal writing, nous is often preferred.

Yes, répondre usually takes à before the thing or person you are responding to.

For example:

• répondre à un e-mail
• répondre à Marie
• répondre à la question

In this sentence, the object is simply not stated. It is understood from the context:

• nous devons répondre aujourd’hui = we must reply today

So the sentence is complete, but if you wanted to specify what you are replying to, you would normally add à.

French uses the present tense here because both ideas are current and immediate:

• Le délai est plus court que prévu = the deadline/time frame is currently shorter than expected
• nous devons répondre aujourd’hui = we currently have the obligation to reply today

This is the normal tense choice for present facts and present obligations.

Yes. The best English translation depends on context.

Le délai can be:

• the deadline
• the time frame
• the time allowed
• the response period

So the French sentence could naturally correspond to several English versions, such as:

• The deadline is shorter than expected, so we must reply today.
• The time frame is shorter than expected, so we have to respond today.

All of these fit the French sentence depending on the situation.