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like vs. as

What's the difference between like and as?

In class here at TestMagic, I encounter such questions routinely; in fact, questions of this type are the most commonly missed questions, and believe it or not, there's a rather simple explanation for why one is wrong and another is right.

Let me ask you a question--when you think about this question, and you think about what's being compared, do you think that it's simply two nouns, or do you think that it's two similar nouns doing similar actions? If it's the latter, we must go with "as," the subordinating conjunction, i.e, the only one that can introduce a sentence.

In this question, the answer to my question seems logical, but in the next it will be more difficult to answer. So, in anticipation of the next question, let me ask you one more thing--in this SC are we comparing simply two nouns or are we comparing two nouns, each with its own verb?

I think in this particular SC it seems *fairly* clear that we are comparing two nouns with two actions, so we should use "as."

So let's look at the next one, which I believe will be a tad more difficult...

I want you to think about this sentence. What would you say naturally?

• :D Genes can jump like pearls.
  

or

• Genes can jump as pearls do.
  

Would you agree that the latter sentence sounds a bit stilted?

Try these sentences:

• :D She walks like duck.
  

or

• She walks like a duck does.
  

You see where I'm headed?

Just in case, let's try one more:

• :D Why are you acting like a fool??
  

or

• Why are you acting as a fool does??
  

Okay, you might have gotten the point by now, but let's compare sentences.

More than thirty years ago Dr. Barbara McClintock, the Nobel Prize winner, reported that genes can “jump” as pearls moving mysteriously from one necklace to another.

You must agree that

as pearls moving.

sounds terrible!!

Let's try again:

More than thirty years ago Dr. Barbara McClintock, the Nobel Prize winner, reported that genes can “jump” as pearls move mysteriously from one necklace to another.

Aaarrgghhh!!! This one's bad because "as" has another meaning here--at the same time. It sounds like the genes are jumping at the same time that the pearls are jumping.

Let's try again...

More than thirty years ago Dr. Barbara McClintock, the Nobel Prize winner, reported that genes can “jump” as pearls do that move from one necklace to another.

This answer, with all due respect, is completely ungrammatical:

"as pearls do" is actually a complete sentence; it should NOT be followed by anything else, don't you agree? Think about it--we could end the sentence there, couldn't we? Yes, we could. So that means we cannot add "that move from one necklace to another" (a noun clause) after it. We could add an adjective/adjective clause, an adverb/adverb clause, but we canNOT add a noun/noun clause.

Whew!!!

Actually, there is so much grammar here that I could explain... If you have any specific questions, I can answer them.