word choice - "Todo list" or "to-do list"

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 a reference by dictionary.com which is different from the use I need for the word.

Which is correct?

Answer

Wiktionary defines both to-do and todo:

Noun
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.

And:

Noun
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.

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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"):

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

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Phrase     guardian.co.uk  bbc.co.uk  nytimes.com  cnn.com
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todo list              16      3,370           27      174
to-do list          2,350     79,000      130,000   30,100
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