Expressing Certainty and Uncertainty

2nd Year Bac · Unit 9 · Functions

Learn to say how sure you are about something — from complete confidence to genuine doubt.

What this function covers

We don’t always feel equally sure about everything we say. English has clear expressions for showing how confident you are — from total certainty to real doubt — which is especially useful when discussing predictions about science, technology, and the future.

عن ماذا تتحدث هذه الوظيفة؟
لا نشعر دائمًا بنفس القدر من اليقين تجاه كل ما نقوله. تحتوي اللغة الإنجليزية على تعابير واضحة لإظهار مدى ثقتك — من اليقين التام إلى الشك الحقيقي — وهو أمر مفيد جدًا عند مناقشة التوقعات المتعلقة بالعلم والتكنولوجيا والمستقبل.

Expressing certainty

Useful phrases

I’m sure / certain / positive that…Definitely.Certainly.Of course.There is no doubt that…It is crystal clear / obvious / evident that…No one can deny that…

Example

I’m quite sure that many of us today can’t live without a mobile phone.
There is no doubt that technology has changed the way we communicate.

Expressing uncertainty

Useful phrases

I’m not sure…I doubt it.I don’t think / guess…It may / might / could…probablypossiblyIt’s unlikely / doubtful that…

Example

I don’t think that robots will be able to replace human beings at work.
Scientists might find a cure within the next decade, but it’s uncertain.

Modals show certainty too

The modal verb you choose is itself a signal of how sure you are — this connects directly to what you learned in an earlier unit.

More certain

must (strong deduction)

Scientists must be close to a breakthrough — they’ve published so many papers.

Less certain

may / might / could (possibility)

This new technology might change the industry completely.

Rewriting sentences — the exam skill

A common exam task asks you to express the same idea using a different certainty expression, without changing the meaning.

Example

“I’m quite sure that many of us can’t live without a mobile.” → “There is no doubt that many of us can’t live without a mobile.”
“I don’t think robots will replace humans.” → “It’s unlikely that robots will replace humans.”

Common mistakes to avoid

⚠️ Watch out

❌ I’m sure about that technology will change everything. → ✅ I’m sure that technology will change everything.

❌ It is obvious that maybe true. → mixing certainty and uncertainty in one phrase — choose one or the other.

❌ I don’t think that robots will can replace humans. → ✅ I don’t think that robots will be able to replace humans. (never stack two modals)

✏️

Your turn — choose the correct expression

1. Which phrase expresses CERTAINTY?
2. Which phrase expresses UNCERTAINTY?
3. Choose the correct sentence.
4. “It is crystal clear that…” shows ___.
5. Which modal shows a STRONG deduction?
6. Choose the correct sentence.
7. “Probably” and “possibly” are used to express ___.
8. Which shows the LEAST certainty?
9. Choose the correct sentence.
10. “No one can deny that…” expresses ___.
11. Which modal expresses POSSIBILITY, not certainty?
12. Choose the correct rewritten sentence for “I’m quite sure that AI is useful.”