"I drink coffee every day."
I wrote "我每天喝咖啡。" and it was marked wrong and insisted on adding a "都" in there, but it is unclear why this is correct or necessary. Does anyone more knowledgeable want to chip in? Is there a big difference in meaning with or without?
To the best of my knowledge, 都 is an intensifier in this situation. It emphasizes the "every." I don't think it's mandatory, though. I'm going to report it.
This explains why 都 is necessary when using 每天 https://resources.allsetlearning.com/chinese/grammar/Emphasizing_quantity_with_%22dou%22
In English, it may seem redundant to have both 每 and 都. But this is the structure we need when speaking/writing Chinese...whether we want it or not ;-)
To remind myself to include both characters, I think of this as "EACH and EVERY day". (As a coffee addict, this is the perfect example sentence for me! Haha!)
AllSetLearning has more examples
I see most of the comments have said 都 is not necessary, but is it wrong? Just making sure its an intensifier.
i think the reason is that, essentially 天 doesn't need a counter word, but 周末 does. but i think you could say 每周末 and it would still make sense
https://resources.allsetlearning.com/chinese/grammar/Expressing_"every"with"mei" discusses the 《每 + Measure Word + Noun + 都》 pattern.