Learn Russian: Мы покупаем четыре нежные лилии и две белые розы. - We are buying four delicate lilies and two white roses.

This highlights the core rule for adjectives modifying feminine nouns after the numbers 2, 3, and 4. While the feminine noun takes the genitive singular form (лилии, розы), the adjective takes the nominative plural form (нежные, белые). If the nouns were masculine or neuter, the adjectives would take the genitive plural instead.

Are the phrases четыре нежные лилии and две белые розы in the nominative or accusative case here?

They are in the accusative case because they are the direct objects of the verb покупаем (we are buying). However, because lilies and roses are inanimate nouns, the accusative forms for the numbers 2, 3, and 4 match their nominative forms perfectly. This inanimate rule applies to the entire number phrase.

Why is the number two written as две instead of два?

The number 2 has two different gendered forms. You use два for masculine and neuter nouns, but две for feminine nouns like роза. The numbers 3 and 4 do not change based on gender, which is why it is simply четыре for the lilies.

Why does the genitive singular of the word for lily end in -ии (лилии)?