Quick answer: The correct spelling is "ditto," not "diddo." Ditto means "the same as previously stated" or is used to indicate agreement without repeating what was already said.
Why the confusion happens
"Diddo" is a common misspelling, likely arising from how the word sounds when spoken quickly or informally, the double "d" sound in the middle can make people guess at "diddo" when writing it down phonetically. There's no alternate accepted spelling, dictionaries only recognize "ditto."
Where the real word comes from
"Ditto" comes from Italian, originally a dialectal form of "detto," meaning "said" (past participle of "dire," to say). It entered English usage in the 17th century, initially in legal and business documents as a way to avoid repeating the same word or phrase multiple times in a list, hence the ditto mark (") still used today to indicate "same as above" in tables and lists.
How to use "ditto" correctly
- As an adverb/interjection expressing agreement: "I think we should leave early." "Ditto."
- As a noun: "Add a ditto mark under the previous entry."
- The ditto mark itself (") is used in written lists specifically to avoid repeating an identical entry directly below a previous one
A simple way to remember the correct spelling
Since "ditto" relates to something being "said" (from the Italian "detto"), remembering this word-origin connection, one "t" sound reflecting "said," can help anchor the correct single-syllable-sounding "dit-" beginning rather than the incorrect double-d "didd-" pattern.
Frequently Asked Questions
Is "diddo" ever an accepted alternate spelling in any dictionary?
No, standard English dictionaries (Merriam-Webster, Oxford, Cambridge) only list "ditto" as the correct spelling.
Is "ditto" formal or informal?
It works in both contexts, though it's more common in casual conversation as a quick way to express agreement than in formal writing, where you'd more often write out the full agreeing statement.
Does "ditto" have any other meanings?
Beyond expressing agreement, it's specifically used in legal, business, and list-making contexts to indicate "the same as stated above," avoiding needless repetition in written documents.
Why English spelling errors like this happen so often
English is full of words where the written form doesn't perfectly match how the word sounds in casual speech, and "ditto" is a good example. When we say it quickly, especially in casual conversation, the "t" sound in the middle can blur slightly, making it genuinely plausible that someone hearing it (rather than reading it) might guess at a "dd" spelling instead. This kind of phonetic-based misspelling is extremely common and isn't a sign of poor language skills, it's simply a natural consequence of English's sometimes inconsistent relationship between spelling and pronunciation.
Other commonly confused word pairs worth knowing
Since you're checking a spelling question, here are several other frequently confused pairs that follow similar patterns, worth bookmarking if you write regularly:
| Correct | Common Mistake | Quick Tip |
|---|---|---|
| Ditto | Diddo | Comes from Italian "detto" (said) |
| Definitely | Definately | Remember "finite" is inside "defi-NITE-ly" |
| Separate | Seperate | Remember "there's A RAT" in sep-A-RAT-e |
| Occasionally | Occassionally | Only one "s," double "c" and double "l" |
| Recommend | Reccomend | Double "m," single "c" |
| Embarrass | Embarass | Double "r," double "s" |
Why using a spell-checker isn't always enough
Modern spell-checkers usually catch "diddo" immediately, since it's not a recognized word at all, unlike some other commonly confused pairs where both spellings are real words with different meanings (like "affect" versus "effect," or "their" versus "there"), which spell-checkers can't always flag since both words exist and are spelled correctly, just potentially used in the wrong context. This is worth keeping in mind broadly: a clean spell-check pass doesn't guarantee you've used every word correctly, only that every word you used is a real, recognized word.
How ditto marks work in practical, everyday writing
Beyond the spoken expression of agreement, the ditto mark (") shows up in specific practical contexts worth understanding if you handle any kind of list-based documentation:
- Grocery or inventory lists: writing "apples" once, then using ditto marks below for repeated identical entries in a column
- Legal and business documents: historically used to avoid rewriting identical addresses, names, or terms repeated across multiple lines
- Bibliographies and citations: some older citation styles use ditto marks or similar notation to avoid repeating an identical author name across consecutive entries
Modern digital documents rely on this convention less than handwritten or typewritten records historically did, but you'll still encounter it in tables, price lists, and certain formal or legal documents.
A broader takeaway about checking spelling before you publish or send something
Whenever you're uncertain about a specific word's spelling, especially one you're about to use in something more permanent (an email to a client, a published article, an official document), a quick dictionary check takes seconds and prevents the kind of small, avoidable error that can otherwise distract from your actual message or, in more formal contexts, subtly undermine your credibility with a careful reader. This is a habit worth building regardless of how confident you generally feel about your spelling, since even strong writers occasionally second-guess certain words, particularly ones borrowed from other languages like "ditto" is.
Why do some borrowed foreign words keep unusual spellings in English?
English has historically absorbed vocabulary from many languages (Latin, French, Italian, Greek, and others) without always adapting the spelling to match typical English phonetic patterns, which is part of why words like "ditto" (Italian), "restaurant" (French), or "psychology" (Greek) can feel like they don't follow standard English spelling logic, they're following the spelling conventions of their language of origin instead.
Bottom line
"Ditto" is correct; "diddo" is a common misspelling with no dictionary recognition. If you're ever unsure about a specific word, a quick dictionary check resolves it faster and more reliably than guessing based on how the word sounds when spoken.
Sources
- Merriam-Webster Dictionary, entry for "ditto"
- Oxford English Dictionary, etymology of "ditto"