Part 3: Conditional Sentences (If-clauses)

1. Zero conditional

We use the zero conditional to talk about things that are generally true, especially for laws and rules. (เราใช้ zero conditional ในการกล่าวถึงสิ่งที่เป็นความจริง โดยเฉพาะกฎหมาย และกฎเกณฑ์ต่าง ๆ)

Examples:

• If I drink too much coffee, I can’t sleep at night.
• Ice melts if you heat it.
• When the sun goes down, it gets dark.

The structure is:

If/When + present simple >> present simple.

1. First conditional

We use the first conditional when we talk about future situations we believe are real or possible. (เราใช้ first conditional เมื่อกล่าวถึงสถานการณ์ในอนาคตที่เราเชื่อว่าเป็นจริง หรือเป็นไปได้)

Examples:

• If it doesn’t rain tomorrow, we’ll go to the beach.
• When I finish work, I’ll call you.

The structure is: 

if/when + present simple >> will + infinitive. 

It is also common to use this structure with unless, as long as, as soon as or in case instead of if. (เราใช้ unless, as long as, as soon as, in case แทน if ได้เช่นกัน)

Examples:

• I’ll leave as soon as the babysitter arrives.
• I don’t want to stay in London unless I get a well-paid job.
• I’ll give you a key in case I’m not at home.
• You can go to the party, as long as you’re back by midnight.

1. Second conditional

The second conditional is used to imagine present or future situations that are impossible or unlikely in reality. (เราใช้ second conditional ในการจินตนาการถึงเหตุการณ์ในปัจจุบันหรืออนาคตที่เป็นไปไม่ได้ หรือไม่เป็นจริง)

Examples:

• If we had a garden, we could have a cat.
• If I won a lot of money, I’d buy a big house in the country.
• I wouldn’t worry if I were you.

The structure is:

 if + past simple >> + would + infinitive. 

When if is followed by the verb be, it is grammatically correct to say if I were, if he were, if she were and if it were. (สำหรับ if clause เราใช้ were กับประธาน he, she, it ได้อย่างถูกไวยากรณ์)

Examples:

• If I were you, I wouldn’t buy this car.
• If Sofia was a prime minister, she would invest more money in schools.
• Ken would travel more if he was younger.

1. Third conditional

Third conditional sentences describe the past. They describe something that didn’t happen. (เราใช้ Third conditional เพื่อบรรยายอดีตที่ไม่ได้เกิดขึ้น)

Examples:

• If I’d studied harder at school, I would have gone to university.

(I didn’t study very hard and I didn’t go to university.)

• Carla wouldn’t have got lost if you hadn’t given her the wrong directions.

(Carla wasn’t given the correct directions and she didn’t find her way.)

• Tina might have finished the exam if she’d had more time.

(Tina didn’t finish the exam and she didn’t have more time.)

The structure is:

 if + past perfect and would + perfect infinitive (e.g. have done).

ทั้งนี้เราสามารถใช้กริยาช่วย (modal verbs) แทนคำว่า would ได้ เช่น could, might, may

เป็นต้น