Sound interchange is divided into two groups: vowel interchange and consonant interchange. With the help of vowel interchange we differentiate parts of speech, e. g. full – to fill, food – to feed, blood – to bleed, etc. In some cases vowel interchange is connected with affixation, e. g. long – length, strong – strength, etc. Intransitive verbs and the corresponding transitive ones with a causative meaning also display vowel interchange, e. g. to rise – to raise, to sit – to set, to lie – to lay, to fall – to fell.