Which one is correct in American English:

This computer program is error-free.

This computer program is error free.

... and why? Are, perhaps, both correct? If so, is there any difference in the meaning? (Aside: we do not speak about "an error{ |-}free program" or "a program free of errors" here. The post-position of "whatever{ |-}free" is intentional.)


3 Answers 3


According to the Chicago Manual of Style § 7.89(3), "[c]ompounds formed with free as second element are hyphenated both before and after a noun." The examples given are "toll-free number" and "accident-free driver."

Specifically, in the construction you listed, the examples are:

"The number is toll-free." and "The driver is accident-free."

Therefore, "The program is error-free." would be the proper construction under the Chicago Manual though other style-guides may say otherwise.


According to this ngram both possibilities are correct, although it might be better to use the hyphen. In British English it is often the case that both forms of a compound are used. Nevertheless, as a trend started more than twenty years ago people tend to use more hyphens in this type of English.


ngram showing usage in the case of predicative use.

  • 1
    @Just_A_Man "error-free", "error free" and "free of error" are synonymous although their place in the noun phrase differs and this is, almost without doubt, true in American English too.
    – LPH
    Mar 23, 2020 at 21:43

Actually, "error free" need not be "error-free" in all cases. The British, especially sources such as the Guardian, prefer "error free" to the latter.

  • 1
    Would help if you gave some examples with links where you found them...
    – fev
    Aug 9, 2022 at 12:27

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