Questions & Answers about Han köper en vit lilja med stora knoppar.
How would I ask what kind of lily he is buying using the vad ... för construction?
You would split the phrase and place the verb and subject in the middle: Vad köper han för lilja? You can also keep the article and say Vad köper han för en lilja?
Why is the adjective vit without an ending, but stora has an -a?
Adjectives must match the nouns they describe. Lilja is a singular en word, so vit stays in its base form. However, knoppar is plural, so stor takes the plural -a ending to become stora.
What is the singular form of knoppar?
The singular is en knopp. Like many en words that end in a consonant, it takes the -ar ending in its plural form.
How can you tell just by looking at the words that lilja is an en word?
There are two clues here! First, it uses the article en. Second, the adjective is vit instead of vitt; if it were an ett word, the adjective would require a -t ending.