The correct phrase is “less than.” In English grammar, “less than” is used to make comparisons between numbers, amounts, distances, or quantities. The phrase “less then” is grammatically incorrect because “then” refers to time, order, or sequence, not a comparison.
- Correct: He spent less than $20 on lunch.
- Incorrect: He spent less then $20 on lunch.
However, when it comes to making comparisons, only one of these phrases is grammatically correct. Let’s break down the rules, look at some clear examples, and learn a quick trick to make sure you never get them confused again.
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The Core Difference: Than vs. Then
To understand why less than is correct, it helps to look at the individual definitions of than and then.
1. What Does “Than” Mean?
Than is a conjunction used specifically for comparisons. It links two or more things when you are measuring a difference in size, amount, quality, or value.
- Examples: Smarter than, bigger than, faster than, and less than.
2. What Does “Then” Mean?
Then is an adverb usually related to time, sequence, or logic. It indicates what happens next, or what occurs as a result of something else.
- Examples: First we eat, then we code. If it rains, then the game is canceled.
How to Use “Less Than” Correctly (With Examples)
You should use less than whenever you are comparing numbers, amounts, distances, or intangible quantities to show that one is smaller or fewer than the other.
Examples in Sentences:
- Money: The movie ticket cost less than $10.
- Time: The meeting took less than an hour to finish.
- Quantity: I have less than half a carton of milk left.
- Abstract Concepts: His second novel was less than impressive.
💡 Quick Summary Rule: If you are comparing two quantities, “than” is your only choice.
Why “Less Then” Is Incorrect
The phrase “less then” is a common spelling mistake (a homophone error) because than and then sound remarkably similar when spoken aloud.
Because then deals with time or sequence, placing it after “less” usually creates a nonsensical sentence. For example:
- Incorrect: I slept less then six hours. (This reads like you slept less, and then you slept six hours.)
- Correct: I slept less than six hours.
The One Rare Exception
The only time “less” and “then” will ever appear next to each other is if a comma separates them as part of a transition in time.
- Example: “Eat less, then exercise more.” In this case, they are two separate thoughts within a sequence, not a single comparative phrase.
Comparison at a Glance
| Feature | Less Than | Less Then |
| Grammatical Status | Correct | Incorrect (in comparisons) |
| Function | Compares quantities, amounts, or values | A common typo / misspelling |
| Key Indicator | Used for measurement (“smaller amount”) | Relates to time, logic, or sequence |
| Example | “This laptop costs less than $500.” | N/A (Avoid this usage) |
Memory Trick: How to Remember the Difference
If you find yourself stuck, look at the vowels in the words to unlock this easy mental shortcut:
- ThAn features the letter A. A stands for Amount or Comparison.
- ThEn features the letter E. E stands for Next (Sequence) or Time.
Since “less” deals with an Amount, always pair it with thAn!
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Frequently Asked Questions
Is it “less than” or “fewer than”?
While both are comparative, use less than for singular or uncountable nouns (e.g., less money, less time, less water). Use fewer than for plural, countable items (e.g., fewer dollars, fewer hours, fewer cups of water).
Why do people mix up than and then?
Because they are homophones, meaning they sound almost identical in casual speech. It is an auditory mistake that easily slips into written text.
Is “less than” acceptable in formal writing?
Yes, “less than” is completely grammatically correct and preferred in academic, professional, and formal writing.
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