Today while watching TV, I came across this sentence,

Don't waste this summer watching TV.

The sentence seemed weird to me because in English grammar if you want to use progressive tense then you should use by, for, before, after etc. One more example:

Puppy fell asleep sucking his thumb.

Shouldn't that sentence have been like this:

Don't waste this summer by watching TV.

And the second one

Puppy fell asleep while sucking his thumb.

But I am only new to English grammar. So if I am wrong, please elaborate.

  • 1
    The sentence is grammatical. When you can take the train, why spend your time driving.? He was allergic to the cat and spent the weekend sneezing. by would be grammatical as well in your example. The joke was so funny, he walked the whole way home laughing. But he did not walk home by laughing. – Tᴚoɯɐuo Apr 10 '18 at 15:26
  • There's no mandatory rule to insert a preposition before the -ing form of a verb. Perhaps, if the -ing form is a noun (i.e., a gerund), you will typically need a preposition. "By watching TV, I learnt about WWII." Watching here is a gerund noun: depending on usage, there may be a need for a preposition. "Watching TV, I learnt about WWII." Here, watching is a present participle that modifies I: it doesn't need a preposition. Wikipedia article has more information on this distinction. – urnonav Apr 10 '18 at 15:39

You don't need to use "by" or "while". These words can add meaning to a sentence but are not always necessary.

This sentence is correct and natural:

Don't waste the summer watching TV.

Commenters have already given other examples:

Why spend your time driving?

He spent the whole weekend sneezing.

He walked home laughing.

By gives the method used:

He got to work by riding his bike.

While means "at the same time"

He ate dinner while watching TV.

Using such words can reduce ambiguity, but they are not strictly required.


I learnt about WWII while watching TV (I was studying and I had the TV on at the same time)

I learnt about WWII by watching TV (I watched tv programs about the history of WWII)

I learnt about WWII watching TV (ambiguous, but probably means the same as "by watching tv" in this context.)

  • 1
    You might check the first few lines of your answer for literals. A couple of slips indicate that you might have been in a hurry – Ronald Sole Apr 10 '18 at 16:55
  • Thanks Ronald, I've edited. If you spot anything else, feel free to correct me. – James K Apr 10 '18 at 17:06

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