英語で“suspect”と“doubt”の違いとは？よくある間違いと使い分けをわかりやすく解説

In English, some verbs about thinking or believing can be confusing.

Two of the most common are suspect and doubt.

These words can seem similar, but they are actually very different in meaning and use.

Let’s explore these two important verbs, learn some related words, and see how to use them naturally.

1. Suspect

To suspect something means you think it might be true, often because of clues or feelings, even if you don’t have proof (things that show something is 100% true).

Examples:

• “I suspect she’s not telling the truth.” (I think she is lying.)

• “He was suspected of stealing the money.” (People thought he stole the money.)

Grammar Tip:

• suspect + that + clause

  “I suspect that he lied.”

• be suspected of + noun/gerund

  “She was suspected of cheating.”

Common Mistake:

A man says something. You think he is not telling the truth.

✘ “I doubt he’s lying” (this means you DON’T THINK he is lying).

✔ “I suspect he’s lying.”

2. Doubt

To doubt something means you think it might NOT be true. It shows uncertainty or disbelief. You’re not sure.

Examples:

• “I doubt she’ll come to the party.” (I think she probably won’t come.)

• “He doubted the results of the test.” (He wasn’t sure they were correct.)

Grammar Tip:

• doubt + that + clause

  “I doubt that he’ll win.”

• In British English, “I doubt it” is often used casually.

  “Will she come?” – “I doubt it.” (I don’t think so)

Common Mistake:

A woman says something. You think he is telling the truth.

✘ “I suspect she’s lying” (this means you THINK she is lying).

✔ “I doubt she’s lying.”

Related Verbs

Here are some similar verbs that help express different levels of belief or uncertainty:

Believe

To accept that something is true.

• “I believe he’s telling the truth.”

Guess

To make a decision or opinion without full information.

• “I guess she’ll be late again.”

Wonder

To think about something in a curious or polite way.

• “I wonder if it will rain today.”

• “I was wondering if you could help me.”

Compare: Suspect vs. Doubt

You think it’s probably true = I suspect he’s lying. (I think he is not telling the truth)

You think it’s probably NOT true = I doubt he’s lying. (I think he is telling the truth)

These verbs are opposites in meaning, so be careful not to mix them up.

Quick Practice

Choose the correct word for each sentence: suspect, doubt, believe, guess, or wonder.

1. I ______ she’ll come on time - she’s always late.

2. Police ______ he was involved in the robbery.

3. I ______ if this old battery still works?

4. She ______ that the offer was real. It seemed too good to be true.

5. I ______ you’re right, but let’s ask the teacher to be sure.

6. He’s acting strangely. I ______ something’s wrong.

Final Thoughts

“Suspect” and “doubt” are useful verbs, but their meanings are very different. One shows belief, the other shows disbelief. By understanding the grammar and context of these words, you can sound more natural and clear in English conversations.

Possible Answers:

1. doubt

2. suspect

3. wonder

4. doubted

5. believe

6. suspect