Based on morphology, Languages in the world can be classified into four types: agglutination, flex, isolation, and incorporation. In the language of agglutination such as Indonesian, there is what-so-called morphophonemic, i.e. the change of sound caused by affixation. One of the features is having prefix me(ng)- on the base verb initiated by phoneme /p/ that turns into phoneme /m/ by the term of assimilation, such as memercayai, not mempercayai. Different from the form memperhatikan, this form comes from the word hati that receives prefix per-, which turns into perhati as the base word. Here per- is not the initial phoneme of base form, so that it is not assimilated. It is also different from the form memerkosa which comes from the base word perkosa. Here per- is not a prefix but a syllable.