The word break chiefly* exists in writing. In this case they say /ɪnʌðənju:z/. This has been happening for millennia. In Pompeii the warning cave canem became (in the hands of an illiterate artisan, making a mosaic 'Beware of the dog' sign) cavec anem.
b
*I'm putting it rather defensively; one could have eternal academic arguments about whether the right adjective would be 'entirely'.