"Non-significant" or "not significant" variable?

@PeterShor's comment is also correct from a statistical point of view. Generally, though, we refer to the significance of a test statistic not a variable since there is no way to test whether a variable is significant, only a relationship, comparison, difference, etc. So, for example, in a regression model of y on x, the coefficient on x is non-significant | not significant. The x variable cannot be significant on its own.

I think of "nonsignificant" as an adjective, but "not significant" as the complement to the copulative "to be". So, "the nonsignificant correlation of sex with the DV..." but "the effect of sex on the DV was not significant." I find awkward "The effect was nonsignificant".