costly
/ˈkɒst.li/
"costly" is a 6-letter English headword indexed on PlainSpell.
The verdict
“costly” is a regularly-used English word, ranked #7,899 in English word frequency and used as an adjective.
- #7,899
- frequency rank, English
- 6
- letters
- 10
- tracked misspellings
- 13
- confusable pairs
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Of high cost; expensive.
Visual similarity to commonly confused words
How many letter changes separate each confused pair (Levenshtein distance, normalized).
Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).
| Property | Value |
|---|---|
| Headword | costly |
| Language | English |
| Part of speech | Adjective |
| IPA | /ˈkɒst.li/ |
| Letters | 6 |
| Frequency rank | #7,899 |
| Misspellings tracked | 10 |
| Confusable pairs | 13 |
| Source | Wiktionary (kaikki.org) |
Where “costly” sits in English frequency
Spelling & Dictionary Insight
The English entry for costly is 6 letters long, classified as an adjective, and transcribed in the International Phonetic Alphabet as /ˈkɒst.li/. Corpus data places it at rank #7,899 in overall English word frequency, indicating it appears regularly in written and spoken text. The dominant gloss from Wiktionary reads: "Of high cost; expensive.".
Our generated misspelling index lists 10 likely wrong-spelling variants for costly, with forms such as "ccostly", "coslty", and "cosstly". Each variant is a distinct typo pattern an edit-distance generator flags, typically a doubled-consonant error, a silent-letter drop, or a vowel substitution. It also participates in 13 confusable-pair relationships, "cosy", "costs", "courtly", and more, where similar look or sound leads writers to substitute one word for another in context.
Etymologically, the entry records: From Middle English costly, costely, costeley, equivalent to cost + -ly. The correct English form is costly, spelled C-O-S-T-L-Y.
Definition
- 1Of high cost; expensive.
Etymology
From Middle English costly, costely, costeley, equivalent to cost + -ly.
Synonyms
Antonyms
This word in other languages
Common misspellings
Also misspelled as: ccostly,coslty,cosstly,costlly,costlyy,costtly,costyl,cotsly,csotly,ocstly
Misspelling Pattern Breakdown
How far each generated variant is from the correct spelling of costly - expressed in single-character edits (insert, delete, or swap one letter). Bigger bars stand out at a glance; a one-edit slip is the hardest to catch.
Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.
Frequently Asked Questions
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Using “costly”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is C-O-S-T-L-Y - every other letter order is a misspelling in standard orthography.
- Say it as /ˈkɒst.li/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
- Don't mix it up with “cosy” - see the side-by-side comparison. costly vs cosy
- Browse more English words and confusable pairs in the same reference. English words
Data Source
Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.