In this sentence, I understand why we use ''a'' as an indefinite article:
''There is a customer who wishes to speak Mrs Winston.''
But I didn't do a great job trying to explain 'why a and not the' to one of my learners (who insisted ''the'' should be used before the noun here)... How do I explain it clearly? She simply didn't see it the way the rest of the class did - that this customer is not some particular, specific customer.
I presented another example ''The customer to whom Mrs Winston spoke is here.'' to try and make it more clear, but that didn't help.
Moreover, she was sulking (a 40 year old student) until the end of the lesson because I said ''the'' should not be used here :-?who
********** NOT A TEACHER **********
Hello, Teacher Lada.
(1) Maybe you could make the sulker happy by telling her that
under the right situation, she would be right!!! That is, if you were
discussing a particular customer, you would use the.
Manager: I hear that there is a customer who wants to speak
with Mrs. Winston. Where is he?
Worker: There [pointing with his hand] is the customer who wants
to speak with Mrs. Winston.
(2) As we say in the United States, it is a win-win situation. You are
correct and your student is correct. It all depends on the situation.
THANK YOU