As
and like are used in a number of different ways and can
be different parts of speech.
'as'
and 'like' - prepositions
As
refers to something or someone's appearance or function. Consider
the following examples:
'Before I became a teacher I worked as a
waiter.'
'I'm going to the fancy dress party as Superman.'
'The sea
can be used as a source of energy.'
The expression 'I've been working as a dog' sounds unusual
because it suggests that you were doing the work of a dog!
Like
has the meaning 'similar to' and is used when comparing things.
Look at these examples:
'I’ve been working like a dog.'
'She looks a bit like her brother.'
'Just like you, I’m always a bit wary of large dogs.'
The
expression 'I've been working like a dog' is idiomatic and
means that you have been working very hard. Note that we can use
adverbs of degree, such as just, very, quite,
not much, not at all, a bit, etc, to modify
like:
'He’s very serious – not at all like his father, perhaps
more like his mother at times.
'as' and 'like' - conjunctions
As
and like can also be used as conjunctions:
As
means 'in the same way that'. Consider the following:
'I always drink tea without milk, just as they do on
the continent.'
'Try to keep your balance on the tightrope, as I do,
by spreading out your fingers like this.'
'The first ten days of July were very wet this year, as
they were last year and the year before.'
In informal English, like is used in the same way. This is
particularly common in American English. Consider the following:
'Nobody else would look after you like I do, baby!'
'She needs the money, like I do, so she works in a bar
in the evenings.'
'I hope you’re not going to be sick again, like you
were when we went to Brighton.
