Fewer refers to a number of individual persons or things.
- Fewer than 50 applicants responded to the recent job vacancy.
Less refers to a quantity of something that cannot be counted as individual items.
- Because of drought, the fields are producing less corn this year.
- Note: If the number is only one, use less.
- One less person attended the meeting.
Lest means for fear that.
- Lest we forget, let’s recognize Tom for his hard work right now.