Questions & Answers about عفوا، أنا لا أشرب القهوة ليلا.
Why do both عفوا and ليلا end with that extra alif and two small dashes (ـاً)?
Those two dashes mark the indefinite accusative case. In Arabic, putting this ending on a noun often turns it into an adverb. عفوا comes from a word meaning "a pardon", so with this ending it acts as "excuse me". ليل means "night", and ليلا means "at night". The extra alif is added as a base to hold the dashes for most words.
If the accusative case gets that extra alif, why doesn't the direct object القهوة have one?
There are two rules preventing it here. First, القهوة starts with ال (the), meaning it is definite. The double dashes are only for indefinite words (words without "the"). Second, even if it were indefinite, words ending in a taa marbuta (ة) never take the extra alif; they just take the dashes directly on top.
Why do we use لا to say "not" here, rather than ليس?
لا is the standard word used to negate present-tense verbs, like أشرب (I drink). You use ليس to negate sentences that don't have a main verb, like "I am not tired" or "the coffee is not hot".
Since أشرب already means "I drink", is the word أنا (I) strictly necessary?
No, it is optional! In Arabic, the verb form already tells you who is doing the action. Including أنا before the verb just adds a bit of emphasis or contrast, similar to saying "Excuse me, I don't drink coffee at night (even if others do)."