May I take your order?

- Yes, please. I'll have a steak sandwich, one fruit salad, and a milk.
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What does 'a milk' mean in the last sentence? A glass of milk?

Yes, but "a milk" isn't correct(although lots of people make the error. Milk is a non-count noun, so "a" is incorrect with it. It's correct to say "a glass of milk" or "a carton of milk" or another expression that's similar.

In the sentence "I'll have a steak sandwich, one fruit salad, and a milk," the phrase "a milk" is not grammatically correct. It seems like the person might be using improper grammar or shortening the phrase "a glass of milk" or "a carton of milk."

To clarify what they mean, you can ask them for clarification. You could say, "Excuse me, could you please clarify what you mean by 'a milk'? Are you referring to a glass or carton of milk?" This way, you can ensure you understand their order correctly.