[Grammar]Like vs. As

Differentiate LIKE and AS

LIKE

The structure of the sentence is usually: VERB + LIKE + NOUN/PRONOUN

• He speaks like a native speaker
• She looks like a supermodel.

AS

The structure of the sentence is usually: AS + SUBJECT + VERB

• Nobody sings as she does.
• They went to the party as they were

It is very common in American English to use LIKE instead of AS. However, it is generally considered informal to use in this way.

• We play football like champions do.

Another use of AS is to say what the role/function of person/thing is

• He started work as a carpenter.
• She used the tapestry as a decoration in her living room

LIKE vs. AS

Be careful, in similar sentences that use LIKE and AS, the meaning of each sentence are very different.  For example:

• As your boss, I must warn your to be careful. (I'm your boss.)
• Like your boss, I must warn you to be careful. (I am not your boss, but he/she and I have similar attitudes.)

AS IF

In English we also use as if to make comparisons. However, it has a few distinct characteristics to its use:

1. The verb after AS IF is always in the past subjunctive, no matter what tense the sentence is.
2. If the verb BE directly follow AS IF, we use were for all personal pronouns.

• He looks as if he knew the answer.

(The verb looks indicates this sentence is in the present - the the verb after AS IF - Knew - is in the past subjunctive).

• She walks as if she were a supermodel.

(The verb after AS IF - be - has been changed to were and not was).

• He boarded the air plane as if he were a seasoned traveler.
• He spends money as if he owned a bank.

Source: http://www.grammar.cl/Notes/Like_vs_As.htm