"a coffee" 文法上正確嗎 ?

你沒有聽錯, May I have a coffee? 是正確的, May I have a cup of coffee? 也是正確的.

Coffee 其實是 countable noun, 也可以是 uncountable noun.

When an uncountable noun is used to classify something, it can be treated as a countable noun. 意思上亦有少許不同. 其他例子包括 lights/light, experiences/experience, fish/fishes, a hair/hair, cake/cakes, wine/wines
記住名詞前或需要配上正確的 articles (a, an, the)

E.g. 以下句子全都正確,
I want a coffee.
Give me two coffees.
I love some coffee.
I love coffee.
I would like a cup of coffee.

She has many experiences.
She has experience in accounting.
She has some experience in accounting.

There are many French wines.
I like wine.

coffee 係 uncountable noun
在noun 要加單位(unit)
正式應係 a cup of coffee

2007-12-29 22:16:55 補充：
基於口語,不需註重文化,再有人講May I have a coffee?

你系唔系聽錯啊
應該系may i have a cup of coffee才對!!!