X
/ɛks/
"x" is a 1-letter English headword indexed on PlainSpell.
The verdict
“X” is in the everyday core of English, ranked #647 in English word frequency and used as a numeral.
- #647
- frequency rank, English
- 1
- letter
- 18
- confusable pairs
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - An unknown quantity or unknown value.
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 | X |
| Language | English |
| Part of speech | Numeral |
| IPA | /ɛks/ |
| Letters | 1 |
| Frequency rank | #647 |
| Misspellings tracked | 0 |
| Confusable pairs | 18 |
| Source | Wiktionary (kaikki.org) |
Where “X” sits in English frequency
Spelling & Dictionary Insight
The English entry for X is 1 letters long, classified as a numeral, and transcribed in the International Phonetic Alphabet as /ɛks/. Corpus data places it at rank #647 in overall English word frequency, putting it firmly in the everyday core of the language. The dominant gloss from Wiktionary reads: "An unknown quantity or unknown value.".
X doesn't appear in our generated misspelling index, suggesting the orthography follows predictable English patterns. It also participates in 18 confusable-pair relationships, "xi", "XL", "XP", and more, where similar look or sound leads writers to substitute one word for another in context.
Etymologically, the entry records: Introduced by René Descartes in the context of mathematical notation, but has since widened to other contexts. The correct English form is X, spelled X.
Definition
- 1An unknown quantity or unknown value.
Etymology
Introduced by René Descartes in the context of mathematical notation, but has since widened to other contexts.
This word in other languages
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
How do you spell "X"?
What does "X" mean?
What words are commonly confused with "X"?
How do you pronounce "X"?
What is the origin of the word "X"?
Is PlainSpell free to use?
Using “X”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is X - every other letter order is a misspelling in standard orthography.
- Say it as /ɛks/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
- Don't mix it up with “xi” - see the side-by-side comparison. X vs xi
- 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.