Look at this electricity bill, Andy.

Question

- Wow! That's a lot.
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In this short dialogue, what is the part of speech of 'a lot'?

1. The electricity bill is a lot.
(Is this sentence grammatical? What other expressions can we use instead of 'a lot'?)

Answer 1

In the dialogue, "a lot" is a noun phrase.
http://dictionary.reference.com/browse/a%20lot?s=t

Sentence 1 is OK, but it'd read better if you write this:
The electricity bill is really high.