Conditional Sentences
Study Guide & Practice Activities
Overview
What are conditional sentences?
Conditional sentences express what happens — or what could happen — when a certain condition is met. They consist of two clauses: an if-clause (the condition) and a main clause (the result). The type of conditional you use depends on how likely, real, or possible the situation is. Mastering conditionals allows you to talk about facts, make predictions, imagine hypothetical scenarios, and reflect on how the past could have been different.
| Type | Purpose | Example |
|---|---|---|
| Zero conditionalIf + present → present | Describe general truths, scientific facts, or habitual outcomes that are always true | If a shark loses a tooth, it quickly grows a new one. |
| First conditionalIf + present → will + verb | Talk about real or likely situations in the future and their probable results | If the polar ice caps melt, sea levels will rise dramatically. |
| Second conditionalIf + past → would + verb | Imagine unlikely or hypothetical present/future situations and their consequences | If California were a country, its economy would rank among the largest. |
| Third conditionalIf + past perfect → would have + p.p. | Reflect on unreal past situations — things that did not happen and their imagined outcomes | If Newton had not observed the falling apple, he might not have developed his theory of gravity. |
Key rules
Common pitfalls to avoid
Comma placement
Use a comma after the if-clause when it begins the sentence. No comma when the if-clause comes second.If it rains, we will stay inside.
We will stay inside if it rains.
No “will” in the if-clause
In future real conditionals, use simple present — not “will” — in the if-clause.If prices will drop, sales will increase.
If prices drop, sales will increase.
“Were” for unreal present
In second conditionals, use “were” for all subjects — including I, he, she, and it.If I was you, I would reconsider.
If I were you, I would reconsider.
Modals add nuance
Replace “will” with “may,” “might,” or “could” to show varying degrees of certainty.If you study, you will pass. (certain)
If you study, you might pass. (possible)
Activity 1
Identify the conditional type
Read each sentence. Choose the letter that identifies the type of conditional.
Activity 2
Match the meaning
Read each conditional sentence and choose the letter that best describes its meaning or function.
Activity 3
Fix the future real conditional
Each sentence has an error with verb forms in the future real conditional. Insert will where needed and fix other verbs. Type the corrected verb phrase for the blank.
Example: If air pollution increases, respiratory diseases become more common. → will become
Activity 4
Choose the correct form (unreal conditional)
Select the letter that shows the correct verb forms to complete each present or future unreal conditional sentence.
Activity 5
Complete the past unreal conditional
Fill in each blank with the correct past unreal conditional form of the verb shown in parentheses.
Example: If Alexander Fleming had not discovered (not discover) penicillin, modern antibiotics might not have existed (might not exist).
Activity 6
Combine into one conditional sentence
Combine each group of short sentences into one conditional sentence using if. You may add, rearrange, or change words, but keep all the ideas.