IF-sentences that connect a condition with a result
📌
Definition
A conditional sentence has two parts: the IF-clause (the condition) and the main clause (the result). If the condition is met, a certain result happens.
There are several types of conditionals. In this lesson, we focus on the two most common real conditionals: the Zero Conditional (facts/truths) and the First Conditional (real future possibilities).
Zero Conditional
100% Real — Always True
IF + Present Simple → Present Simple
"If you heat water to 100°C, it boils." "If I eat sugar, I feel energetic." "If plants do not get water, they die."
First Conditional
Real — Future Possibility
IF + Present Simple → Will + base verb
"If it rains tomorrow, I will stay home." "If you study hard, you will pass." "If she calls, I will answer."
🎯
Lesson Objectives
Form and use the Zero Conditional (IF + Present Simple, Present Simple).
Form and use the First Conditional (IF + Present Simple, will + base verb).
Understand the key difference: Zero = always true; First = real but uncertain future possibility.
Use UNLESS as a more emphatic alternative to "if not."
Know when to use a comma and when to omit it.
Avoid the most common errors in conditional sentences.
2
Zero Conditional — Always True
Scientific facts, natural laws, habits, and universal truths
Both verbs are in the Present Simple. The result ALWAYS happens when the condition is met — no exceptions.
If you heat ice, it melts.
If water reaches 100°C, it boils.
If plants do not get sunlight, they die.
If I drink coffee late at night, I cannot sleep.
1 — Scientific Facts and Natural Laws
"If you mix blue and yellow, you get green."
"If an animal does not eat, it dies."
"If you drop a ball, it falls."
These are 100% true — they happen every single time, without exception.
2 — Personal Habits and Routines
"If I eat too much, I feel sick."
"If she works until midnight, she is always tired the next day."
"If he exercises in the morning, he has more energy all day."
These are personal patterns or truths — things that always happen for this particular person.
3 — General Truths
"If people do not sleep enough, they feel tired."
"If students do not study, they do not understand the material."
"If you practice every day, your English improves."
General truths are not personal but apply to people in general — still 100% reliable.
💡 WHEN = IF in Zero Conditional
In the Zero Conditional, you can often replace IF with WHEN — the meaning stays the same.
"If I drink coffee, I feel energetic." = "When I drink coffee, I feel energetic."
This is because the result happens EVERY TIME — so WHEN (every time) = IF (in all cases).
3
First Conditional — Real Future Possibility
Things that might happen — if the condition is met, the result is likely
First Conditional Structure
IFPresent Simple (condition),will + base verb (result)
The condition uses Present Simple. The result uses will + base verb. The condition is real and possible — it may or may not happen.
If it rains tomorrow, I will stay at home.
If you study hard, you will pass the exam.
If she is late, we will start without her.
If he does not call, I will not wait for him.
1 — Real Future Possibilities
"If we leave now, we will arrive on time."
"If she applies for the job, she will probably get it."
"If the weather is nice, we will go to the beach."
The speaker believes the condition is genuinely possible — maybe 50% chance or more. The result will follow if it happens.
2 — Warnings and Threats
"If you touch that, you will burn yourself."
"If he does not stop, he will get in trouble."
"If you do not pay, we will cancel your account."
First Conditionals are commonly used for warnings — the speaker warns that a consequence will follow a certain action.
3 — Promises and Offers
"If you help me today, I will help you tomorrow."
"If you come to the meeting, I will introduce you to the team."
"If you need anything, I will be right here."
Promises and offers are also common First Conditionals — the speaker commits to a result if the condition happens.
⚠️ Critical Rule — Do NOT use WILL in the IF-clause
❌ "If it will rain tomorrow, I will stay home." → WRONG
✅ "If it rains tomorrow, I will stay home." → CORRECT
The IF-clause uses Present Simple to talk about the future condition. WILL only goes in the result clause.
4
The Comma Rule
When to use a comma — and when not to
✏️
Comma Placement in Conditionals
The comma rule applies to BOTH the Zero and First Conditional:
IF-clause FIRST → Use a comma between the two clauses:
"If it rains, I will stay home."
Result clause FIRST → No comma needed:
"I will stay home if it rains."
Both orders are grammatically correct — only the comma placement changes.
5
UNLESS — If Not
A powerful alternative to "if not" — with emphasis on the exception
📌 UNLESS = IF + NOT
UNLESS+Positive Present Simple,Result
Unless you study, you will fail. = If you do not study, you will fail.
Unless it rains, we will go to the park. = If it does not rain, we will go to the park.
Unless you are on time, the bus will leave without you. = If you are not on time, the bus will leave without you.
Unless she calls me, I will not go. = If she does not call me, I will not go.
⚠️ IMPORTANT: UNLESS is already negative — do NOT add NOT after it. "Unless you do NOT study" is WRONG. Say: "Unless you study."
6
Zero vs First Conditional — Full Comparison
Every key difference in one table
Feature
Zero Conditional
First Conditional
Meaning
Always true — fact, law, habit
Real future possibility
IF-clause tense
Present Simple
Present Simple
Result clause tense
Present Simple
Will + base verb
Certainty
100% certain — always happens
Possible — maybe 50% or more
Can replace IF with WHEN?
Yes → "When I eat sugar, I feel energetic."
No → "When it rains, I will stay home." ❌ (implies certainty)
Example — Affirmative
"If you heat water, it boils."
"If you study, you will pass."
Example — Negative
"If you do not water plants, they die."
"If she does not hurry, she will miss the bus."
Example with UNLESS
"Unless you water plants, they die."
"Unless she hurries, she will miss the bus."
7
Common Mistakes to Avoid
The most frequent conditional errors
If it will rain tomorrow, I will stay home.
If it rains tomorrow, I will stay home.
Rule: Never use WILL in the IF-clause of the First Conditional. The IF-clause uses Present Simple, even when referring to the future.
If you will study, you will pass.
If you study, you will pass.
Rule: Same issue — IF + Present Simple (condition). "If you will study" has a double future — wrong structure.
Unless you don't study, you will fail.
Unless you study, you will fail.
Rule: UNLESS is already negative ("if not"). Adding "don't" creates a double negative and reverses the meaning. UNLESS + positive verb.
If you mix blue and yellow, you will get green.
If you mix blue and yellow, you get green.
Rule: Scientific facts and universal truths → Zero Conditional: both verbs in Present Simple. "You will get" sounds like a future prediction, not a fact.
If she calls, I answer. (future plan)
If she calls, I will answer. (future plan)
Rule: For future possibilities or plans, use the First Conditional. Zero Conditional is for facts/habits, not predictions about specific future events.
I stay home if it rains tomorrow.
I will stay home if it rains tomorrow.
Rule: For specific future predictions/plans (First Conditional), the result clause needs WILL + base verb, not just Present Simple.
If you study, unless you will pass.
If you study, you will pass. / Unless you study, you will fail.
Rule: IF and UNLESS cannot both appear in the same sentence. They serve the same function (introducing the condition) and replace each other.
Unless it will be cold, I will wear a jacket.
Unless it is cold, I will wear a jacket.
Rule: UNLESS follows the same rule as IF — use Present Simple in the condition clause, not WILL. "Unless it is cold" = "If it is not cold."
8
Audio Examples — Listen & Repeat
All structures across both conditionals and UNLESS
🟢 Zero — FactIf you heat water to one hundred degrees, it boils.Universal scientific truth
🟢 Zero — HabitIf I drink coffee late at night, I cannot sleep.Personal habit — always true
🔵 First — PredictionIf you study every day, you will improve quickly.Real future possibility
🔵 First — WarningIf you do not leave now, you will miss the train.Warning about a consequence
🟣 UnlessUnless you hurry, we will be late for the meeting.UNLESS = IF + NOT
🟣 UnlessUnless it stops raining, we will cancel the event.= If it does not stop raining
🔵 First — PromiseIf you help me, I will help you in return.Promise — First Conditional
🟢 Zero — Reversed orderPlants die if they do not receive enough water.Result clause first — no comma needed
9
Reading Passage
Zero Conditional (green), First Conditional (blue), Unless (violet)
🟢 Zero Conditional🔵 First Conditional🟣 Unless
The Coffee Farm
Tarrazú, San José (Mountain Coffee Region), Costa Rica 🇨🇷
Carlos is a coffee farmer in the Tarrazú region of San José province — one of the most famous coffee-growing areas in the world. He knows that good coffee does not happen by accident. He always tells his children: "If you take care of the soil, the plants grow strong.If the plants grow strong, the beans taste better." These are the rules of farming that never change.
Every year, Carlos plans carefully for the harvest season. "I grow the best coffee in this region," he says, "but if we do not get enough rain this year, the harvest will be smaller than usual." He watches the weather closely. He knows from experience that if the temperature drops too much at night, the plants do not produce well.
This year, Carlos is worried. The rainy season arrived late. He tells his son Marco: "If it rains enough next month, we will have a good harvest.Unless the clouds come soon, we will have to irrigate the whole field by hand — and that will cost us a lot of money."
Marco is young and enthusiastic. He asks his father: "What will happen if we introduce new coffee varieties on the south side of the farm?" Carlos thinks carefully. "If the new plants survive the first season, we will see results in two years.Unless we choose the right variety for this altitude, we will waste time and money. You have to be patient in farming."
Carlos also shares his knowledge with tourists who visit the farm. He explains: "If you pick the beans when they are red, the coffee is much sweeter.If you roast them too long, they lose their flavor." He smiles and adds: "If you taste our coffee today, you will never want to drink anything else."
By the end of the visit, Carlos feels proud. He knows that if you respect the land, the land gives back to you.Unless the whole country protects its agricultural traditions, future generations will lose something precious. For Carlos, the coffee farm is not just a business — it is a way of life.
📖 Reading Comprehension Quiz
Answer the questions based on the reading passage above.
10
Grammar Practice Quiz
Test your knowledge of Zero and First Conditionals — 20 questions
