Fleeting Vowels is the sixty-sixth (assuming read left to right) skill in the language tree for Russian and it teaches the "fleeting vowel" phenomenon through three lessons.
Grammar Notes[]
This is the result of how some feminine nouns work with genitive plural. Ordinarily a feminine noun would just drop the 'a' at the end of the word to make it genitive plural. eg. книга -> книг. But some nouns would be awkward to pronounce if the vowel was just dropped. So an 'o' or an 'e' is inserted before the final consonant to make it easier to pronounce.
Fleeting vowels occur whenever a vowel is added or removed due to a change in case. This only occurs with o and e:
- An o or e is added in between two consonants when switching from a nominative noun ending in a vowel to a genitive (especially plurals)
- Тарелка --> тарелок
- Чашка --> чашек
- The same o or e is removed when switching back or when it exists in an ending like -ец and is declined to another form.
- Американец --> 2 американца
- 5 бутылок --> 4 бутылки
Lessons[]
Lesson 1: Ending in -ок[]
- банок = jar(s)
- бутылок = bottle(s)
- коробок = box(es)
- вилок = fork(s)
Lesson 2: Ending in -ек/-ец[]
- кружек = mug(s)
- ложек = spoon(s)
- ручек = pen(s)
- колец = ring(s)
Lesson 3: New words with fleeting vowels[]
- кусок = piece
- испанка = Spanish woman
- испанец = Spanish person
- перец = pepper
Reference[]
Duolingo Lesson: www.duolingo.com/skill/ru/Fleeting-Vowels