Conditionals Lesson: Definition, Rules & Examples

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Updated: Mar 13, 2025

Lesson

Lesson Overview

What Is a Conditional Sentence?
Types of Conditional Sentences
Common Student Questions & Mistakes (and Tips!)
Examples and Practice Questions

Conditionals are an essential part of English grammar, allowing us to express possibilities, hypothetical situations, and their consequences. In this lesson, you will learn what conditionals are, their structure, and how to use them correctly. We will explore the five main types: Zero, First, Second, Third, and Mixed Conditionals, along with clear explanations and examples. You will also discover common mistakes learners make and how to avoid them. By the end of this lesson, you will confidently create conditional sentences to express real and unreal situations, improving both your spoken and written English.

What Is a Conditional Sentence?

A conditional sentence is a sentence with a condition and a result. It shows that one thing depends on another. Key points to remember:

A conditional sentence has two parts: the if-clause (condition) and the main clause (result).
The if-clause states the condition (often beginning with if or unless) and the main clause states what will happen if that condition is met.
Example: If I study hard (condition), I will pass the test (result). – The result "I will pass the test" only happens if the condition "I study hard" is true.
"Unless" can be used instead of if...not. (Example: "Unless it rains" means "If it does not rain.")

Why use conditionals? They help us talk about cause and effect, make plans, discuss facts, or imagine different situations. Conditional sentences are common in everyday life – from science facts to making promises and talking about dreams or regrets.

Don't Forget To Take This Quiz!

Conditional Sentences Quiz: Test Your Grammar Skills

Types of Conditional Sentences

In English, there are four common types of conditional sentences. Each type has a different use and verb form. We'll explore each one with definitions, structures, and examples:

Type	When Do We Use It?	Structure (Form)	Example Sentence
Zero Conditional (Type 0)	Facts and general truths (100% always true).	If + present tense, ... present tense.	If you heat water to 100°C, it boils. (This is always true.)
First Conditional (Type 1)	Real possibilities in the present or future.	If + present tense, ... will + base verb.	If you study, you will pass the test. (A likely future result if the condition happens.)
Second Conditional (Type 2)	Unlikely or imaginary situations in the present or future.	If + past tense, ... would + base verb.	If I had wings, I would fly. (Imagines something not true now.)
Third Conditional (Type 3)	Unreal situations in the past (imagining a different past; 0% possibility now).	If + had + past participle, ... would have + past participle.	If I had known, I would have come earlier. (Imagines a different past – in reality, I didn't know, so I came late.)

Let's break down each type in a bit more detail:

1. Zero Conditional – General Truths

Use: To talk about facts, rules, or things that are always true.
Structure: If + present tense, ... present tense (both clauses use simple present).

Example 1: If you mix red and blue, you get purple.
Example 2: If you freeze water, it becomes a solid.

2. First Conditional – Real Possibilities

Use: To talk about real and possible situations in the present or future.
Structure: If + present tense, ... will + base verb.

Example 1: If you run quickly, you will catch the bus.
Example 2: If it rains, we will stay inside.

3. Second Conditional – Unreal or Hypothetical Present/Future

Use: To talk about imaginary, unlikely, or wishful situations in the present or future.
Structure: If + past tense, ... would + base verb.

Example 1: If I had a million dollars, I would buy a pet elephant.
Example 2: If I saw a spider in my bathroom, I would cry out loud.

4. Third Conditional – Unreal Past Situations

Use: To talk about hypothetical situations in the past – things that did NOT actually happen in the past, and to imagine different outcomes for those past events.
Structure: If + had + past participle (past perfect), ... would have + past participle.

Example 1: If I had known about the party, I would have gone.
Example 2: If they had visited us, we would have spent a wonderful evening together.

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Conditional sentences quiz

Common Student Questions & Mistakes (and Tips!)

Why can't I use will in the if-clause? – Use present tense in the if-clause, not "will."
Tense consistency: Don't mix up structures (e.g. "If I win the lottery, I would buy a car" should be "If I won the lottery, I would buy a car").
"Unless" means "if not" – Don't use a double negative ("Unless you don't hurry..." should be "Unless you hurry...").
Punctuation: If the if-clause comes first, use a comma before the result clause ("If I finish my homework, I can watch TV.").
"If I was" vs. "If I were": In second conditional, formal English prefers were ("If I were taller...").