if

if — conjunction

1. This word introduces a necessary situation — the result you describe can take pl

1.連接詞A1
釋義

This word introduces a necessary situation — the result you describe can take place only after that situation has happened first.

例句

If it rains tomorrow, Manuela will take the bus to work.

if + present, main clause with will for real future

The cake will rise properly only if you add enough eggs to the mixture.

main clause + only if + condition clause

同義詞
反義詞
  • whether or not

    means the result is the same regardless of the condition

文法句型

if + present tense, … + will + base verb

if + past tense, … + would + base verb

if + past perfect, … + would have + past participle

if + present, … + present (zero conditional for general truths)

用法筆記

In conditional clauses, do not use 'will' or 'would' inside the if-clause itself ('If it rains…' not 'If it will rain…'), except in polite requests (sense 6). For unreal or imaginary situations in the present, the past subjunctive form 'were' is used for all subjects ('If I were you…'), though 'was' is common in informal British English.

常見錯誤

❌If it will rain, we will stay home.
✅If it rains, we will stay home.
💡The if-clause takes present tense, not 'will,' even when the meaning is future.
❌If I would be rich, I would travel the world.
✅If I were rich, I would travel the world.
💡The second conditional uses past tense (or 'were') in the if-clause, never 'would.'
❌If trust the internet for answers, you may get wrong information.
✅If you trust the internet for answers, you may get wrong information.
💡The if-clause needs a subject.

2. You use this word to show that something is true, even though another fact might

2.連接詞B2
釋義

You use this word to show that something is true, even though another fact might suggest the opposite — often to admit a weakness while keeping your main point.

例句

The meal was delicious, if a little too salty for my taste.

if + adjective phrase after a positive statement

Sari is a kind person, if sometimes quick to get angry.

同義詞
  • although

    more common and less formal; can start a sentence

  • though

    even more conversational than 'although'; often placed at the end

  • even if

    stronger contrast; suggests the limitation does not change the outcome

文法句型

if + adjective/adverb

if + clause

用法筆記

This sense always appears after a positive statement and introduces a limitation or weakness. It is common in written British English but less frequent in casual American speech. The clause after 'if' is usually shortened to an adjective or adverb phrase.

常見錯誤

❌If it was cold, we went for a walk.
✅We went for a walk, if it was cold.
💡Sense 2 requires the concessive 'if' to appear after the main positive statement, not before it.

3. You use this word to say that one thing always happens immediately after or as a

3.連接詞B1
釋義

You use this word to say that one thing always happens immediately after or as a result of another thing happening — like saying 'every time' or 'whenever.'

例句

If the doorbell rings, the dog starts barking loudly.

if = whenever: a habitual reaction

Sade takes three deep breaths if she feels nervous before a test.

if = every time: describing a personal routine

同義詞
  • whenever

    clearer and more precise for this meaning; preferred in modern usage

  • every time

    more emphatic; used in speech

  • when

    casual; can replace 'if' in this sense in everyday conversation

文法句型

if + present, … + present

用法筆記

Distinguish from sense 1: sense 3 describes a reliable pattern ('every time X happens, Y happens'), while sense 1 describes a one-time possibility ('if X happens, Y will happen'). In sense 3 both verbs are usually in the present tense and the main clause never contains 'will.'

常見錯誤

❌If it will rain, the roof leaks.
✅If it rains, the roof leaks.
💡Sense 3 does not use 'will' in either clause; it states a regular fact.

4. You use this word when you accept something as true for the moment and then say

4.連接詞B1
釋義

You use this word when you accept something as true for the moment and then say what follows from that — often before stating an opinion, a reaction, or a decision based on that fact.

例句

If you have already finished your homework, you may go outside to play.

if = since / given that: accepting a completed action

If Ravindra's story about the delay is correct, the train should arrive at noon.

if + accepted premise, conclusion follows

同義詞
  • since

    more direct; sounds more confident about the premise

  • given that

    formal; used in academic or analytical writing

  • assuming

    shifts focus to a hypothesis rather than an accepted fact

文法句型

if + clause (accepted fact), main clause

用法筆記

This sense differs from sense 1 in that the condition is already accepted as true, not hypothetical. It often occurs with 'then' in the main clause and is very common in reasoning and argument. A good test: replace 'if' with 'since' or 'given that' and the sentence should still make sense.

常見錯誤

❌If you are here already, I will call you later when you arrive.' — The second half contradicts the first because the premise ('you are here') is accepted.
✅If you are here already, let us start the meeting.
💡The conclusion follows naturally from the accepted premise.

5. You use this word after verbs such as ask, know, wonder, or tell to introduce a

5.連接詞B1
釋義

You use this word after verbs such as ask, know, wonder, or tell to introduce a question that has two possible answers — like 'yes' or 'no' — without using a direct question form.

例句

Christopher asked if the library was open on Sunday afternoons.

ask + if: indirect yes/no question

I wonder if Yael has received my email about the conference.

同義詞
  • whether

    more formal; preferred before infinitives and 'or not'

  • whether or not

    emphasizes both possibilities equally

文法句型

verb + if + clause (indicative)

verb + if + not + clause

用法筆記

In this sense 'if' and 'whether' are often interchangeable, but 'whether' is preferred (a) before infinitives ('whether to go'), (b) after prepositions ('the decision about whether'), and (c) when 'or not' follows immediately ('whether or not'). In short, everyday indirect questions, 'if' is more common in both British and American English.

常見錯誤

❌He asked me that I wanted coffee.
✅He asked me if I wanted coffee.
💡Indirect questions use 'if' or 'whether,' not 'that.'
❌I wonder that she will come.
✅I wonder if she will come.
💡'Wonder' is not followed by 'that'; it requires 'if' or 'whether.'

6. You use this word to make a request, offer, or suggestion sound more polite and

6.連接詞A2
釋義

You use this word to make a request, offer, or suggestion sound more polite and less direct, often with words like 'could,' 'would,' 'may,' or 'might.'

例句

If you could pass me the salt, that would be great.

if you could + verb: polite request at the table

I was wondering if you might have time to look at my report.

同義詞
  • whether you'd like

    used in very formal offers, e.g. 'I wondered whether you'd like to join us'

文法句型

if + pronoun + would/could + verb

if + I + may/might + verb

if + you + could + verb

用法筆記

This is one of the few cases where 'will' or 'would' can appear inside the if-clause ('If you would like…,' 'If you could…'). In very formal British English 'if you would be so kind as to…' is used. In everyday speech, 'if' can be omitted in short polite phrases: 'Could you pass the salt?' is already polite without 'if.'

常見錯誤

❌If you can pass me the salt.' (too direct — sounds like a condition, not a request)
✅If you could pass me the salt.
💡'Could' makes it polite.

if — noun