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B2 · English Grammar

Conditional
Conjunctions

You can use the lab as long as you book it first — and take a key in case the door is locked.

unless · as long as in case · once · since
The idea

Conditions without if

Each of these conjunctions introduces a condition, but each adds something extra: a requirement, a precaution, a moment, or a reason.

Examples

We'll be late unless we hurry.

Call me once you arrive at the station.

The shared rule

unless / once / in case

+ present tense

Never will or would inside the condition clause.

Requirement

unless · as long as · provided that

unless = except if  ·  as long as / provided that = only if

You'll miss the train unless you hurry.  = if you don't hurry
You can use the lab as long as you book it first.  everyday
The grant continues provided that the team reports yearly.  formal

The clause after unless is positive: never unless you don't...

Precaution & timing

in case · once · since

in case = because it is possible that  ·  once = at the moment something happens  ·  since = because it is true that

Take a map in case you get lost.  precaution
Once the funding arrives, we start phase two.  certain event
Since the equipment is set up, we can finish early.  reason

Here since means because — it is not about time.

Don't confuse them

in case vs. if

in case
a precaution

I'll take an umbrella in case it rains.

I take it now — maybe it never rains.

if
a reaction

I'll take an umbrella if it rains.

I take it only when the rain starts.

If you can add "just to be safe", you need in case.

⚠ Watch out

Common mistakes

Unless you don't hurry, you'll be late.

Correct: Unless you hurry, you'll be late.

Once you will arrive, call me.

Correct: Once you arrive, call me.

Provided that you will pay, we'll deliver.

Correct: Provided that you pay, we'll deliver.

I'll phone you in case I arrive.

Correct: I'll phone you when I arrive.

Now it's your turn

Let's
practice.

Say the answer out loud — then tap to check.

Practice 1
tap the blank to reveal

Fill the gap

You can borrow my laptop (only if) you give it back tonight.
Take a jacket (because it is possible that) it gets cold later.
We will publish the paper (at the moment something happens) the results arrive.
You will miss the train (except if) you hurry.
We can finish early (because it is true that) the equipment is set up.
Practice 2
tap a sentence to reveal the error

Spot the mistake

You can borrow the car provided thatA you will returnB it byC six andD fill the tank.

Byou will return → you return

✓ no will after provided that

Take a jacket in caseA it getsB cold, becauseC the evenings here is chillyD in October.

Dthe evenings here is chilly → the evenings here are chilly

✓ the evenings is plural → are

Unless you don't hurryA, we will missB the last train andC have to walkD home.

AUnless you don't hurry → Unless you hurry

✓ unless is already negative

Practice 3
tap to reveal a model answer

Complete the sentence

I'll save you a seat as long as
Take some cash with you in case
Once the exams are over,
We won't get a table unless
Speak & write

Your turn

Use the conjunction in bold in your answer.

unless — What could stop your plans this week?
as long as — What can a friend borrow from you, and on what condition?
in case — What do you always carry with you as a precaution?
once — What's the first thing you'll do when today's work is finished?
Recap

Remember this

unless
except if · clause stays positive
as long as / provided that
only if · the one condition
in case
because it is possible that · precaution
once / since
at the moment · because it is true

No "will" or "would" inside the condition clause.

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