Why is it "девяностОлетний", but "сорокАлетний"?
Isn't it like the linking vowels in Russian are only "о" and "е"?
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Sign up to join this communityWhy is it "девяностОлетний", but "сорокАлетний"?
Isn't it like the linking vowels in Russian are only "о" and "е"?
These are the rules for declining composits with the first numeral root. We use the genitive in this case but not a connecting vowel:
Одиннадцать → одиннадцати
Двадцать → двадцати
Тридцать → тридцати
Сорок → сорока
Пятьдесят → пятидесяти
Шестьдесят → шестидесяти
Семьдесят → семидесяти
Восемьдесят → восьмидесяти
Еxceptions: один (однолетний), девяносто (девяностолетний), сто (столетний), тысяча (тысячелетний). In these cases we use connecting vowels.
Sourse: Розенталь, «Справочник по правописанию и литературной правке» (М. , 1978), 37 page, 6 point.