Expressing certainty, probability, doubt

This lesson covers common expressions used to show how sure or unsure we are. You will learn phrases and modal verbs that indicate certainty (100%), probability (high to low), and doubt (low probability or disbelief). We focus on tone and situational appropriateness for business and everyday contexts.

• Certainty: expressions and structures that show you are sure (e.g., I'm certain, there's no doubt, must + verb).
• Probability: degrees of likelihood using modals and adverbs (e.g., probably, likely, might, could).
• Doubt: ways to show skepticism or low probability (e.g., I doubt, unlikely, may not).

Select an expression that matches how sure you really are and use the correct grammatical form.

• Use modals (must/might/could) + base verb to express degrees of deduction or possibility.
• Use adverbs (definitely/probably/possibly) before the main verb (or after 'be').
• Use phrases (I doubt / I'm certain / I'm confident) to state personal attitude; these are followed by a clause (that + clause) or an infinitive where appropriate.

Match intensity (certain → probable → doubtful) to the context — in business, avoid absolute certainty unless you are certain.

Avoid these universal errors that confuse meaning or tone.

• Mixing modals incorrectly (e.g., using must and might together) which creates unclear meaning.
• Placing adverbs in the wrong position (e.g., after the verb when they should be before or after 'be').
• Using absolute language in uncertain contexts (e.g., 'definitely' when you only have a guess).
• Overusing vague words (maybe, perhaps) in formal business communication instead of precise probability language.
• Confusing adjectives and adverbs (e.g., 'probable' vs 'probably').

Check modal choice, adverb placement, and tone to make your level of certainty clear and appropriate.