Questions & Answers about La novena clase es difícil.
Why is the word for 'ninth' novena here instead of noveno?
Ordinal numbers act like adjectives, so they have to match the gender of the noun they describe. Because clase is a feminine noun, the masculine noveno changes its ending to become the feminine novena.
Why does novena come before clase? I thought adjectives usually go after the noun.
You are right that most describing words go after the noun in Spanish. However, ordinal numbers (like first, second, ninth) are an exception. They almost always go before the noun, just like in English.
clase ends in an 'e'. How do we know it is feminine?
Nouns ending in 'e' do not have a strict rule for gender, so their gender has to be memorized. The feminine article la and the feminine ordinal number novena give you clues in this sentence that clase is feminine.
Why do we use es instead of está here?
Since is feminine, why doesn't change its ending to match it?