I'm trying to come up with a regex that will match only words that do not contain special characters. In the following string:

one two:two three four five:five six

I want to match one, three, four, and six only. I want to exclude the two:two and five:five.
`/[a-zA-Z]+/` matches these words, but it also matches "two", "two", "five" and "five" since it just treats the ":" as a separator for another word.

Any ideas?