First and second conditional
กฎ
A conditional sentence connects a condition clause to a result clause, expressing real, imaginary, or past scenarios.
A Conditional sentence establishes a direct causal or hypothetical relationship between a condition clause (introduced by if or unless) and a main result clause. The three foundational conditionals at Level B1 are: (1) Zero Conditional (Universal Truths & Habits): Evaluates general scientific laws, automatic mechanical responses, and permanent habits. Formula: If / When + Present Simple, Present Simple. Examples: "If you freeze water, it turns to ice", "If I drink coffee late at night, I cannot sleep". (2) First Conditional (Real Possibilities in the Future): Evaluates an authentic condition that has a realistic probability of occurring in the future. Formula: If + Present Simple, will / can / might + bare base verb. Examples: "If the weather stays warm, we will have a barbecue in the garden", "If you don't hurry, you will miss the morning train". (3) Second Conditional (Hypothetical / Unreal Present or Future): Evaluates an imaginary or improbable scenario contrary to present facts. Formula: If + Past Simple, would / could / might + bare base verb. Examples: "If I won a million pounds, I would travel around the world", "If he exercised regularly, he would feel healthier". Clause Reversal Rule: The if-clause can appear first or second. When the if-clause begins the sentence, a comma separates the clauses ("If it rains, we will stay home"). When the main clause comes first, no comma is used ("We will stay home if it rains").
จำไว้
- Zero conditional expresses universal truths: if you heat ice, it melts.
- First conditional expresses realistic future results: if it rains, we will cancel the picnic.
- Second conditional expresses hypothetical scenarios: if I had more free time, I would learn Spanish.
กับดักที่พบบ่อยและควรเลี่ยง
Unless means if not, so do not add a negative verb after it: say unless it rains, never unless it doesn't rain.
Guía visual
How to read this B1 topic
At B1, grammar links ideas: condition, result, reported meaning, experience, and narrative order.
1. Name the relationship
Ask whether the sentence gives a condition, contrast, cause, report, or result.
If it rains, we will stay home.
2. Separate time from aspect
Finished event, visible result, duration, and background action use different forms.
I had left before she arrived.
3. Test both clauses
In complex sentences, the second half often proves the first half.
I wish I knew.
Conditional patterns
Read both halves. The result clause often tells you which condition pattern is needed.
| Meaning | If-clause | Result clause | Example |
|---|---|---|---|
| general truth | present simple | present simple | If water freezes, it expands. |
| real future | present simple | will + base verb | If it rains, we will stay. |
| imaginary present | past simple | would + base verb | If I knew, I would tell you. |
| imaginary past | past perfect | would have + participle | If I had known, I would have called. |
Contrasts that often decide the answer
Event or background
Simple forms move events forward; continuous forms show an action in progress.
I left while she was talking.
Fact or stance
Modals, hedges, and reporting structures show how certain or responsible the speaker sounds.
This may indicate a problem.
Clause or compressed phrase
Advanced writing often compresses full clauses into participle, noun, or prepositional phrases.
Having reviewed the data, we revised the plan.
ตัวอย่าง
- 1If you heat water to one hundred degrees Celsius, it boils and produces steam.
- 2If we finish our quarterly project report early, we will celebrate with dinner.
- 3If I were twenty years younger, I would definitely learn how to skydive.
- 4She will miss the express train to Birmingham unless she leaves the house right now.
- 5What would you do if you lost your passport in a foreign country?
- 6If the sun shines brightly tomorrow, the family will spend the day at the beach.
- 7If he had a dependable car, he would drive to work instead of taking the bus.
- 8When people do not get enough sleep, they often feel irritable and fatigued.
- 9We would gladly help you repaint the living room if we had more free time.
- 10If you touch that boiling kettle with your bare hands, you will burn yourself.
ข้อยกเว้น
Unless vs. If Not: The subordinating conjunction unless means if not. Do not use a negative verb after unless: "Unless you leave now, you will be late" (means "If you do not leave now"). Subjunctive Were: In the Second Conditional, standard formal English uses were rather than was for all subjects, particularly in the set phrase of advice: "If I were you, I would take the job offer."
ข้อผิดพลาดที่พบบ่อย
(1) Will in the condition clause: "If it will be sunny, we will go out." → "If it is sunny, we will go out." (The if-clause requires the present simple). (2) Would in the condition clause: "If I would know the answer, I would tell you." → "If I knew the answer, I would tell you." (Second conditional condition requires past simple). (3) Comma placement error: Putting commas when the result clause precedes the if-clause.
ทดสอบตัวเอง
Write one zero conditional rule, one first conditional plan, and one second conditional dream, then practise.
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