These two words are pronounced exactly the same, spelled almost the same, and confused constantly — even by careful writers. The difference comes down to one letter and two very different meanings.
The Short Answer
Complimentary relates to praise or to something given free of charge.
Complementary relates to things that go well together or complete each other.
If you can replace the word with free or flattering, use complimentary. If you can replace it with matching or completing, use complementary.
What Does Complimentary Mean?
Complimentary has two connected uses:
1. Expressing praise or admiration
She made several complimentary remarks about his presentation.
The review was entirely complimentary — not a single criticism.
2. Given free of charge
This meaning grew from the idea of doing something as a courtesy or gesture of goodwill.
The hotel offered complimentary breakfast to all guests.
He received two complimentary tickets to the show.
The airline provided complimentary headphones on long flights.
Both meanings share the same root: a compliment, whether verbal or in the form of a gift.
What Does Complementary Mean?
Complementary describes things that work together, complete each other, or make a stronger whole when combined.
Red and green are complementary colors — they sit opposite each other on the color wheel.
The two business partners had complementary skills: one handled design, the other handled finance.
Ginger and lemon have a complementary flavor profile that works well in tea.
The word comes from complement — meaning something that completes or perfects another thing.
You also see it in specific fields:
- Complementary angles in geometry: two angles that add up to 90 degrees.
- Complementary medicine: treatments used alongside conventional medicine, such as acupuncture or herbal therapy.
- Complementary DNA in biology: a strand that pairs with another.
The One-Letter Difference Worth Knowing
| Word | Spelling clue | Core meaning |
| complimentary | contains pli (like compliment) | praise or free |
| complementary | contains ple (like complete) | completing or pairing |
Memory trick: Complement completes — both words contain the letters c-o-m-p-l-e. If you’re talking about things that complete each other, you need the e.
Where Writers Go Wrong
The most common mistake is writing complimentary when the intended meaning is completing or matching.
❌ The colors were complimentary to each other.
✅ The colors were complementary to each other.
❌ The therapy is a great complementary treatment for stress. (if you mean it’s free)
✅ The therapy is a great complimentary treatment for stress.
The confusion is understandable — the words are homophones. You’ll never mishear them in speech, but in writing the distinction matters.
Quick Test Before You Write
Ask yourself what you mean:
- Free of charge? → complimentary
- Full of praise? → complimentary
- Goes well with something else? → complementary
- Adds up or completes something? → complementary
One more check: swap in the word complete. If the sentence still makes sense, use complementary. If it doesn’t, use complimentary.
The flavors complete each other. ✅ → complementary
The breakfast is complete. ❌ → complimentary
Both words are correct English — they just do different jobs. Once the distinction clicks, you’re unlikely to mix them up again.
Read more:
- Dialog vs. Dialogue: Is There a Difference?
- Offence vs Offense: What’s the Difference?
- Woman vs. Women: What’s the Difference?
- Verbage or Verbiage: Which Word Is Correct?
It’s Afini, I am the author at Vocab press, a website focused on animal facts with clear visuals and simple guides. I research and share accurate, easy-to-understand information for readers of all ages. My goal is to make learning about animals fun, trustworthy, and simple. I follow fact-based writing and keep content updated, helpful, and people-first. Thank you for reading.
