If / Unless: a specific condition for an outcome

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On this page:
If / Unless
Emphasis
Tense Agreement
Connectors – Condition v. Outcome
Only If
Only If / If Only
Even if / Whether
Practice

If / Unless

Expressing a specific condition for an outcome

If / Unless

IF		UNLESS
If introduces a clause with a condition (one of many) to achieve a specific outcome. The (dependent) clause may be placed before or after the the main (independent) clause.		Unless (if...not) introduces a (dependent) clause with a condition that is an exception to achieving the outcome in the main clause.
OUTCOME You will have a tender turkey.	IF if you cook it slowly	OUTCOME You will have a tender turkey	EXCEPT IF / IF NOT unless you overcook it.
You will have a tough turkey.	if you overcook it	You will have a tough turkey	unless you cook it slowly.
We'll arrive at 8:00.	if our train is on time	We'll arrive at 8:00	unless our train is late.
We'll bring some champagne.	if you wish.	We'll bring some champagne.	unless you object.

Emphasis Clause Order

EMPHASIS PLACEMENT	STANDARD PLACEMENT
The if or unless-clause can be placed before the outcome clause for emphasis. A comma is placed after the first clause.	When the if-clause or unless-clause is placed after the main clause (medially), no particular emphasis is intended. NO COMMA is used.
If you wish, we'll bring some champagne.	We'll bring some champagne If you wish.
Unless you object, we'll bring some champagne.	We'll bring some champagne unless you object.

Tense Use

PRESENT / PAST	FUTURE
When discussing habits or routines, the present or the past tense can be used in conditioned statements. See Pres-Past Conditions.	However, when discussing future plans, the present tense is used to refer to the future in the unless-clause or if-clause.
We usually arrive at 8:00 if our train is on time. We usually arrived at 8:00 if our train was on time.	We will arrive at 8:00 if our train is on time. *We will arrive at 8:00 if our train will be on time. Use present tense instead.
We always arrive at 8:00 unless our train is late. We always arrived at 8:00 unless our train was late.	We'll arrive at 8:00 unless our train is late. *We'll arrive at 8:00 unless our train will be late. Use present tense instead.

*Yellow highlighting indicates example of incorrect usage.

Connectors for Condition vs. Outcome

CONDITION	OUTCOME
If / only if / unless / provided that (a conjunction) introduces a clause with a specific condition to achieve an outcome.	Otherwise / or else (if...not) introduces a clause with a the likely outcome if you do not do the action in the clause or sentence before it.
If you use a thermometer, This is one way to tell when it's ready. There may be other ways as well.	you will know when your turkey is done.
Only if you use a thermometer, There is only one way to tell when it's done. (Specifically, use this way.)	will you know when your turkey is done.
Provided that you use a thermometer, There is only one way to tell when it's done. (Specifically, use this way.)	you will know when your turkey is done.
Unless you use a thermometer, Not using a thermometer will give bad results. (Listen to me!)	you won't know when your turkey is done.
Use a thermometer.	Otherwise, you won't know when your turkey is done. (Introduces an independent clause)
Use a thermometer,	or else you won't know when your turkey is done.

Note: Sometimes, using the negative form is a way for the speaker to impose his/her will. Compare: "Are you tired?" and "Aren't you tired?". The speaker, when using the negative, wants the listener to agree.

Only If

Word Order – Transposition

Only IF (at the beginning of the sentence)

CONDITION	OUTCOME
When only if is placed at the beginning of a sentence, it introduces the clause with the condition (in the same way that if does.)	However, the outcome clause differs. Note that the auxiliary verb moves in front of the subject in the only-if clause.
If you dry your dishes with a towel,	they will be spotless!
Only if you dry your dishes with a towel,	will they [will] be spotless!
If you use Zing dish soap,	you get really clean dishes.
Only if you use Zing dish soap,	do you [do] get really clean dishes. (get = do get)
If you used Zing dish soap,	you got really clean dishes. (got = did get)
Only if you used Zing dish soap,	did you [did] get really clean dishes.

A Condition vs. A Wish

ONLY IF	IF ONLY
Us only if to indicate the one condition required to achieve a desired effect. (under one condition) When used at the beginning of the sentence the auxiliary verb is moved before the subject.	Use if only to express a wish – one that you are doubtful about actually happening. The result clause is optional and is separate. It is more emphatic than I wish…
Only if you dry your dishes with a towel, will they be spotless!	If only I had more time! I could relax.
Only if you clean up your room, will you find your lost jeans.	If only you would clean up your room. You would find your lost jeans.
Your windows will be clean enough to see your face only if you wash them with Zing!	If only I had some Zing window cleaner.
I will please my mother-in-law only if my house is clean.	If only I could please my mother-in-law.
I am happy only if you are here. / Only if you are here, am I happy.	If only you were here!
She was pleasant only if we told her what she wanted to hear.	If only he hadn't told his mother everything.

Also see Wishes (only if)

Even if & Whether or not

EVEN IF		WHETHER OR NOT
Even if introduces a clause with a challenging or negative condition. The speaker is saying that no condition will stop the outcome. Even if emphasizes the speakers intent to achieve the outcome or goal without regard for a difficult or negative condition.		Whether or not introduces a dependent clause in which the condition or its alternative does not stop the completion of the outcome in the main clause. That is, if the condition exists or if the condition does not exist, the outcome will or must happen anyway. Whether can be split apart from or not by the subject and verb phrase of the clause. See If / Whether
OUTCOME I'll help you	CHALLENGING CONDITION even if I don't have much time.	OUTCOME I'll help you	THE CONDITION DOESN'T MATTER whether or not I have much time.
I like to walk to work	even if it is raining.	I like to walk to work	whether it is raining or not .
Your father loves you	even if your father doesn't say it	Your father loves you	whether or not he says it.
He'll get his work done	even if he has to work all night.	He'll get his work done	whether or not we wants to work all night.

alternative (n.) – something you can choose to do or use instead of something else
Also see even if Adverbs of Emphasis

Practice

Road Rules

Select the answer that best completes the sentence. Pay attention to the punctuation in the sentence.
Check your answer by clicking the "check button" to the right.

#	YOUR RESPONSE	ANSWER AND FEEDBACK
1.	Most drivers will let you change lanes you signal well in advance.
2.	You shouldn't change lanes you signal first.
3.	A driver may change lanes it is safe to do so.
4.	A driver should stop and check for oncoming traffic before making a right turn on a red light; , he will cause an accident.
5.	A driver may make a right turn on a red light it is a one-way street and the traffic is oncoming.
6.	A driver can go through a red light a police officer signals the driver to do so.
7.	A driver may drive 65 mph in a zone that is marked 65 mph it is unsafe to do so.
8.	Drivers must be careful; , accidents will happen.
9.	you put your full attention on driving, will you lower your chances of having an accident.
10	A driver should park in a handicapped space the driver has a special permit.
11.	When parking, a driver should park between the marked lines. , he will take up two spaces.
12.	A driver should look carefully before opening his door on the traffic side of the street, oncoming traffic may hit the door.