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I always thought it was a todo list, and quite a few places online refer to it as todo, but various spell checkers are telling me it should be to-do.

The only meaning I could find was which is different from the use I need for the word.

Which is correct?

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4 Answers 4

up vote 15 down vote accepted

Wiktionary defines both to-do and todo:

to-do (plural to-dos)
2. A task that has been noted as one that must be completed, especially on a list.
My to-do list has been growing longer every day.


todo (plural todos)
(US) A task yet to be done; an item on a to-do list.

You can use whichever you want, but be consistent. To-do is a little clearer, but hyphens are naturally lost as languages evolve (to-day, wire-less), so todo should be fine too.

Edit: Waggers makes a very good point that todo isn't yet as widely adopted as to-do. So you may be better off sticking to to-do.

Ngram of "todo list" vs "to do list" (+ "list" because to avoid the fuss and commotion meanings, and "to do" will include "to-do"):

to do list vs todo list

Comparison of term on newspaper websites, but note "to-do list" also returns hits for "to do list":

todo list              16      3,370           27      174
to-do list          2,350     79,000      130,000   30,100
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A search for to-do also has zero results, so I don't think Google Ngram Viewer works for "to-do list". In fact, books containing "to-do list" are returned under an Ngram search for "to do list". – ShreevatsaR Oct 25 '11 at 9:38
@ShreevatsaR Well spotted! I'd read the results the wrong way around as well. "To do list" seems to match for "to-do list". – Hugo Oct 25 '11 at 9:41
@ShreevatsaR: Search Ngrams for "to - do list" (put spaces around the hyphen) and it'll work. To-do seems the most popular by far. – Daniel Oct 25 '11 at 19:29
@drɱ65δ: Interesting… So both "to do list" and "to - do list" match "to-do list", but "to-do list" doesn't? How are we to make sense of Ngram results? :-) – ShreevatsaR Oct 25 '11 at 19:44

The OED has to do and to-do, but not todo. Todo looks like an extinct bird to me.

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What years do they have in the OED for the task meaning? – Hugo Oct 25 '11 at 9:11
The earliest citation for a to-do list is dated 1921, from a US source. – Barrie England Oct 25 '11 at 9:30

While "todo" is found in some dictionaries (such as Wiktionary) it is less common in more established dictionaries such as the Collins English Dictionary, and the entry in the Chambers 21st Century Dictionary only lists the hyphenated form. While Hugo is correct that often the language evolves and hyphens are eventually dropped, this process takes time and at present todo is not widely recognised as a single word in the way that "today" and "wireless" are. Indeed, this Google Books N-gram illustrates this very clearly:

Google Books Ngram of "todo list" versus "to-do list"

I would therefore advise against using "todo" and side with the spell-checkers.

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How do you know those to-dos in the Ngram are listed tasks and not a fuss or commotion? But this other Ngram of "todo list" vs. "to-do list" shows you're right, to-do is still by far the most common. And some searches over some newspaper websites confirm this. – Hugo Oct 25 '11 at 9:00
@Hugo Thanks, duly corrected. – Waggers Oct 25 '11 at 9:02
See ShreevatsaR's comment on my answer: we read the Ngram results the wrong way round, and "to-do list" doesn't return any results. Use "to do list" instead. – Hugo Oct 25 '11 at 9:46

In short, both are correct. Though in the purest sense, it could be that neither are.

Most dictionaries seem to contain only the classical definition ("a disturbance or fuss") rather than the modern one that most people use today ("something to be completed"). I was unable to find any "task" definition other than in Wiktionary and The Free Dictionary; at least online, it's missing from the New Oxford American Dictionary, Collins English Dictionary, Chambers 21st Century Dictionary, Merriam-Webster, Cambridge Online Dictionary, and Longman Dictionary of Contemporary English. Can anyone confirm this?

According to the Online Etymology Dictionary, To-do came into use in the 1570's, meaning "proper or necessary to be done". A newer meaning emerged in the 1820's, being "a disturbance or fuss". I saw someone quote a 1920's figure for a resurgence of the "task" meaning, but according to the N-Grams it looks like that didn't happen until at least the 80's.

The few dictionaries that recognize the "task" meaning generally consider both to-do and todo as proper. Though as others have noted here, to-do is vastly preferred by formal publications; only in the programming world and some informal contexts does todo seem to be more common.

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In to-do/todo list, the term is an adjective. All that you have to say about the noun "todo" is irrelevant here, and just muddies the water. – Drew May 19 at 20:06
@Drew I apologize if I added to the confusion. Though to be fair, I haven't found any relevant dictionary entries for a noun, adjective, verb, whatever. Which at least supports my argument that it's not a word recognized by a proper language authority, and is a slang term left up to personal interpretation as dictated by popular use (hence everyone's mad dash to use n-gram searches). – Beejor Jun 12 at 23:44

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