Which to use
“castle” is a noun and “costly” is an adjective - they look or sound alike but fill different roles in a sentence.
- #3,282
- “castle” frequency rank
- #7,899
- “costly” frequency rank
- 11181
- confusion score
Side-by-Side Comparison
| Feature | castle | costly |
|---|---|---|
| Definition | A large residential building or compound that is fortified and contains many defences; in previous ages often inhabited by a nobleman or king. Also, a house or mansion with some of the architectural features of medieval castles. | Of high cost; expensive. |
Where the spellings diverge
Shared letters are muted; the letters that actually set castle and costly apart are highlighted. They share 4 letters in sequence, which is exactly why the eye skips the difference.
Spelling & Dictionary Insight
castle and costly form a confusable pair in the English index, two distinct headwords that are easily confused because they look alike, sound alike, or both. They share most of their letters but differ in 2 positions - close enough that the eye skips over the difference, far enough that meaning fully diverges. Our composite confusion score for this pair is 11181, derived from the frequency rank of both members and their visual similarity.
castle is recorded at frequency rank #3,282, classified as anoun, pronounced /ˈkɑːsəl/. costly is at rank #7,899, tagged as anadj, pronounced /ˈkɒst.li/.
Glosses for this pair are partially populated in our dataset, but the full side-by-side definitions above should still guide you to the right choice.
With a confusion score of 11181, this pair ranks #488,457 of 530,003 scored English confusable pairs - a relatively easy-to-tell-apart pair.
Frequency comparison
Frequently Asked Questions
Can "castle" and "costly" be used interchangeably?
Remembering castle vs costly
The fastest way to pick the right one every time.
- Check the role first: if you need a noun, it's “castle”; for an adjective, it's “costly”.
- See each word in full, definition, IPA, etymology and its other confusables. Full “castle” entry
- Browse more pairs most likely to be confused. Most confusable