Breakdown of Почему ты всегда наливаешь только глоток чаю?
чай
tea
ты
you (singular)
всегда
always
только
only
Questions & Answers about Почему ты всегда наливаешь только глоток чаю?
Why is the word for tea written as чаю instead of the regular genitive чая?
This is the Partitive Genitive (sometimes called the Second Genitive). Some masculine uncountable nouns, mostly foods and liquids, can take a -у or -ю ending instead of the standard -а or -я when talking about a quantity or a portion of it. Here, because we are talking about a specific amount (глоток, a sip), we can use чаю.
Would it be wrong to say глоток чая instead?
Not at all! Using the standard genitive чая is perfectly correct and actually more common in standard modern Russian. The -ю ending gives the sentence a slightly more conversational or traditional feel, but you can always safely use чая.
Why doesn't the ending of глоток change if it is the direct object of the verb?
The word глоток (a sip or gulp) is indeed the direct object of наливаешь (you pour), meaning it is in the accusative case. However, because it is an inanimate masculine noun, its accusative form looks exactly the same as its dictionary (nominative) form.
Why is the verb наливаешь in the imperfective aspect here?
The adverb всегда (always) tells us this is a repeated, habitual action. In Russian, habitual actions require an imperfective verb, which is why we use наливаешь instead of its perfective counterpart.