Double-click on any word and see its definition from Cambridge Dictionaries Online.

The word as is very flexible, and can be used in many different ways.

As can be used for comparison, in the following ways:

Before a prepositional phrase:

			In Argentina, as in Australia, they eat a lot of meat.
			In the 2nd World War, as in the first, millions of civilians were killed.

Followed by a clause:

			When in Rome, do as the Romans do.
			He eats as the Portuguese do – a small breakfast and then a great big lunch.

http://andromeda.rutgers.edu/~jlynch/Writing/l.html#like

In similes (writer's or speaker's references to things with comparison between them and what is being discussed):

			He was as red as a beetroot.
			I'm feeling as fresh as a daisy.

http://www.bbc.co.uk/education/listenandwrite/similes/whatiss.htm

As can also be used in the same way to express inequality:

			I don't get paid as much as she does.
			The weekend wasn't as sunny as the week days before it.

http://www.edufind.com/english/grammar/ADJECTIVES10.cfm

The word as can also be used to talk about the function, job or role of a person or thing:

			We can use this knife as a screwdriver.
			I used to work as a shop assistant.
			His greatest performance was as Professor Higgins in Pygmalion.

As can also be used in the same way as "because":

			As he refused to behave himself, I had to send him to the headmaster.
			I stayed at home, as it was raining all day.

We also use as after certain verbs followed by an object, and certain verbs in passive forms:

			They described him as a pleasant man who liked to help others.
			I see her as a bad influence on the other children.
			She was never thought of as a good actress at school.
			He was recognised as the country's greatest leader.

As is also used in some common expressions:

			Please phone me as soon as you can.
			His dog is aggressive as well as stupid.
			You can go out as long as you come home before midnight.
			As far as I am concerned, we can proceed.

http://www.wsu.edu/~brians/errors/asfaras.html

For more information on different uses of as see:

To see hundreds of examples of the different uses of the word as, see the Web Concordancer:

http://vlc.polyu.edu.hk/scripts/concordance/WWWConcappE.htm

Just type as into the 'search string' field, select any corpus in the 'select corpus' field, and then click on the 'search for concordances' button.