 For example, the English suffix "-s" is pronounced when it follows a voiceless phoneme ("cats"), and when it follows a voiced phoneme ("dogs").This type of assimilation is called "progressive", where the second consonant assimilates to the first; "regressive" assimilation goes in the opposite direction, as can be seen in "have to" .English no longer has a productive process of voicing stem-final fricatives when forming noun-verb pairs or plural nouns, but there are still examples of voicing from earlier in the history of English