Questions & Answers about السؤال الأول سهل، والثاني صعب.
Why does الثاني keep the letter yaa at the end here, when similar words sometimes drop it?
الثاني belongs to a category of words called defective nouns (Ism Manqus) because its root ends in a weak letter. These words keep their final yaa when they have the definite article ال, just like in this sentence. If it were indefinite, the yaa would be dropped and replaced with a double kasra, becoming ثانٍ.
How does the grammar show that سهل means 'is easy' rather than 'the easy first question'?
In Arabic nominal sentences, the subject is usually definite and the predicate is indefinite. Here, السؤال الأول is definite, but سهل is indefinite (it lacks ال). This break in definiteness tells you it is the predicate. If it were an adjective modifying the noun, it would have to match in definiteness: السؤال الأول السهل.
Is it grammatically required to drop the word for 'question' in the second half of the sentence?
No, it is not strictly required, but it is highly preferred for natural style. Just like in English, Arabic commonly omits the noun in parallel structures when the context is already established. Saying والسؤال الثاني صعب is grammatically correct but sounds unnecessarily repetitive compared to simply using والثاني.
If the subject were a feminine noun like المشكلة (the problem), how would the ordinal numbers change?