1.It weighs about a pound.

"about" is a preposition here.

No, it's an adverb, an intensifier for the noun phrase, 'a (=one) pound'. (Quirk, Greenbaum et. al. 7.62)
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How can I get the book youhave mentioned written by "Quirk, Greenbaum ".

I am from India. Is this book available in India?

Thanks a lot for your quick and thoughtful answers.
It's not available in Japan, Hanuman-- but with the internet, I can and do order books from everywhere.

A Comprehensive Grammar of the English Language, Quirk, Greenbaum, Leech & Svartnik (Longman 1985), ISBN 0-582-51734-6, is quite expensive.

A Student's Grammar of the English Language, Greenbaum & Quirk (Longman 1990), ISBN 0-582-05971-2, is a paperback, shortened version of 'A Comprehensive Grammar'. It lacks many of the examples, but is very much cheaper.

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