The Mongolian language is said to be agglutinative, in the sense that it adds suffixes to a basic morpheme to clarify the meaning of a word. The principle called vowel harmony stipulates that vowels of different classes (anterior or posterior) cannot found in the same concept. In other words, a name cannot be composed of anterior and posterior vowels because the affixing of the suffixes will over according to the class of vowels found in the basic morpheme. To better understand this process, let's take a few examples.
a) Маргааш tomorrow → Маргаашнаас from tomorrow
b) Өнөөдөр today → Өнөөдөрөөс from today
c) Монгол Mongolian → Монголоор in Mongolian
d) Франц french → Францаар in french
e) Зав free time → Завтай with free time
f) Ав- take → Авсан took
g) Оч- visit → Очсон visited