Learners' Questions: 'As...as' expressions

Mohammad Tariq from Arghanistan wants to know what part of speech 'as...as' is. Dan has the answer.
Watch this video to find out the answer and test your understanding in our quiz here: ...
TRANSCRIPT
Dan
Hi guys! Dan here for BBC Learning English with this week's Learner Question. Find out what it is after this.
OK! So, this week's learner question comes from Mohammad Tariq from Afghanistan, and he writes: Hello! I hope you are in the best of health. Would you kindly tell me what parts of speech as... as are. I know that we use adjectives or adverbs between them, but I do not know what they are themselves. Kind regards.
OK Mohammed Tariq, I found an answer as quickly as I could. Now, this structure is used to measure and compare things that are similar in proportion, and you're right about the adjectives and adverbs going between the as…as. The first as functions as an adverb and modifies the following adverb or adjective. The second functions as a preposition when connected to noun or a pronoun, or as a conjunction when it relates to a following clause, such as in the sentence: I found an answer as quickly as it was possible to do.
Now I like to think I'm as good a dancer as Michael Jackson. OK,OK, maybe not as good a dancer, but did you notice the use of the adjective and the noun? …as good a dancer as Michael Jackson. When we use an adjective and a noun between an as…as expression, we must remember the article. …as good a dancer. And this is also true for an …as delicious an orange as…
To make these expressions negative we put not before the as…as. For example: he was not as smart as his sister. And in negative expressions we can replace the first as with so. For example: he was not so smart as his sister.
These expressions are idiomatic and they're very, very common in English. We have a few set ones which people tend to repeat over and over again. For example: When I saw the ghost, I went as white as a sheet. Or: In the library be as quiet as a mouse. Or: I was late for work. I ran He ran as fast as lightning.
I hope that answers your question Mohammed Tariq. If anybody else out there has a question, please email it to us at [email protected]. And for more information go to bbclearningenglish.com. Thank you very much! See you next time on Learners' Questions.