Meaning of CON- in English

con- This prefix is pronounced stressed BrE AmE kɒn AmE \ kɑːn (1) if the following syllable is unstressed ( ˌ confron ˈ tation) , (2) in many two-syllable nouns ( ˈ contract, but con ˈ trol) ; and (3) in context, when contrastively stressed ( ˌ uni ˌ formity and ˈ con ˌ formity) . Otherwise it is usually weak kən in Received Pronunciation and General American, though strong in some regional British speech (con ˈ sider) . Before a stem beginning n , one n is lost (con ˈ nect, ˌ conno ˈ tation) .

Longman Pronunciation English Dictionary.      Английский словарь произношений Longman.