Covert, related to cover,
has historically been pronounced [kuhv-ert] /ˈkʌv ərt/ (Show IPA)
with [uh] /ʌ/
the same stressed vowel found in cover.
This [uh] /ʌ/
is the traditional and unchallenged vowel in many other English words spelled with stressed o
followed by v,
or a nasal in the same syllable, words of high frequency like love
and above, mother
and other, some
The adjective covert, however, by analogy with overt [oh-vurt, oh-vert] /oʊˈvɜrt, ˈoʊ vərt/
its semantic opposite, has developed the pronunciation [koh-vert] /ˈkoʊ vərt/
perhaps because of the frequent coupling of the two terms in the news media. This is now the more common pronunciation for the adjective in American English, though not in British English, which retains the historical pronunciation. For the noun senses, less likely to appear in the news or to be contrasted with overt
and its [oh] /oʊ/
sound, the historical [kuhv-ert] /ˈkʌv ərt/
remains the more frequent pronunciation.