"Opposed" or "apposed"

Should it be apposed or opposed in testing for non failure as apposed to success?

I initially thought it should be apposed, because opposed seems to suggest opposition. Interestingly Chromium flags apposed as an unknown word!

Solution 1:

It should be "opposed". "Apposed" would mean sitting next to each other instead of diametrically opposed, as failure and success are.

Solution 2:

Most people won't know the word appose, but Robusto's answer is correct here, and Ben is wrong.

Both words ultimately derive from Latin positum - to put, but imported separately from French - which added the a- prefix ("towards") to give appose. The Latin ob- prefix ("against") became oppose.

Appose originally meant to apply (as, a seal to a document), but now it means to lay alongside or in proximity (as, the cut edges of a wound being stitched up). It's a rare word which as Colin Fine says is more likely to occur as an error for "opposed" than to be used correctly outside of specialised formal contexts where it only refers to spatial proximity of physical objects.

Oppose has a long history of use with a broad stretch of meaning, ranging from deadly feuds to mundane comparisons (as OP's example, definition 3: to contrast or counterbalance).

Those who feel they can justify using apposition in the "metaphorical" sense of critical juxtaposition of concepts are simply mistaken. The purpose of language is to communicate effectively: not one in ten readers would apprehend the significance of the a- prefix meaning alongside, as opposed to the o- prefix meaning opposite, in contrast. It would be poor use of language to thus confuse them.