Deciding whether to use “less” or “fewer” can be quite a task. While both words indicate a reduction, their correct usage depends on countability, and the distinction is especially important in formal writing and academic contexts.

Use “fewer” with plural, countable nouns — items that can be counted individually.

✅ The revised policy led to fewer errors in data collection.

Use “less” with singular, uncountable nouns — concepts, quantities, or masses that are measured rather than counted.

✅ We experienced less resistance during the second phase of the project.

Tricky Exceptions to Note:
1. Time, money, distance, and weight — though technically measurable, are often treated as uncountable.

✅ The journey took less than three hours.
✅ They spent less than $100 on supplies.

2.Set expressions often override strict grammar:

✅ He is less than impressed by the outcome.
✅ She’s less likely to accept the offer.

In Formal English, especially in academic or professional writing, misuse of “less” instead of “fewer” can be marked as an error.

❌ Informal:
There were less students in class today.
✅ Formal:
There were fewer students in class today.