is that so
"is-that-so" is a 8-letter English headword indexed on PlainSpell.
The verdict
“is that so” is uncommon English (outside the top frequency list), classed as a phrase. The kind of spelling people second-guess.
- Unranked
- below top-frequency English
- 10
- letters
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - Really? Is it true?
| Property | Value |
|---|---|
| Headword | is that so |
| Language | English |
| Part of speech | Phrase |
| Letters | 10 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “is that so” sits in English frequency
Rare enough to double-check
is that so is uncommon English outside the top frequency list, classed as aphrase. Rarity is why readers land here mid-draft. Gloss: "Really? Is it true?".
is that so has no tracked misspelling variants, a straightforward case of a spelling with little room for common typos. Our confusable-pair dataset has no match for it, which usually means its spelling is distinct enough that readers don't reach for a similar-looking word instead.
This headword's origin isn't recorded in our source data, leaving phoneme-to-grapheme mapping as the best guide to its spelling rather than a borrowing history. The correct English form is is that so, spelled I-S- -T-H-A-T- -S-O.
Definition
- 1Really? Is it true?
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). See the methodology for how each field is sourced and updated.
Frequently Asked Questions
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Using “is that so”
The practical upshot for anyone who landed here from a spell-check.
- The one correct English spelling is I-S- -T-H-A-T- -S-O - every other letter order is a misspelling in standard orthography.
- 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.