Question: Which sentences are natural? (Unless you know for certain that only one of them would be natural, in which case: Which sentence is natural?)
1 and 3 are okay; 2 and 4 aren’t.
Use of washing requires more:
Don’t forget to finish washing before you eat. is the closest fit for your example I can get, though the context sounds a little strange.
Alternative examples:
Don’t forget to wash the clothes before you go out.
Finish the washing before you go out.
Did you have to wash the dishes this morning?
Were you washing the dishes this morning?
Your reply reminded me of the difference I read in a textbook too. This just tells me that I have to use the language more, textbooks are not everything.
…a nd to answer the question. ‘Don’t forget to wash your hands’ sounds most natural. ‘Washing’ is used in the question format.
Don’t forget to wash your hands.
Have you finished washing your hands?
No, not with that question. When I said ‘washing is used in the question format’ I didn’t mean to imply that it was always used or that it was exclusively used in that format.
I completely forgot -coming- here when I was a kid.
I’ll never forget -hearing- this piece of music for the first time.
Above two sentences indicate that the verb ‘forget’ can accept gerund after it.
Then how is “Don’t forget washing your hands before eating.” wrong?
Please comment. Thanks.
I completely forgot washing my hands when I was a kid - correct
I completely forgot to wash my hands when I was a kid - would be correct without ‘completely’.
Don’t forget washing your hands - incorrect
I don’t forget coming here when I was a kid. - incorrect.
I’ll never forget washing my hands for the first time. - correct (though implausible!)
I’ll never forget to wash my hands for the first time. - would be correct without ‘for the first time’.
I don’t forget hearing this piece of music for the first time. - incorrect
It might help to know that some verbs can take either the gerund or the infinitive. ‘Forget’ ‘remember’ and regret’ are examples. Very broadly the gerund (ing form) is used when we are talking about things people did and the infinitive is used when talking about things people are/were supposed to do.
Examples: I forgot to lock the door. I’ll never forget climbing that mountain
I remembered to lock the door. I remembered shutting the door.
I regret to tell you that you have failed. I regretted telling you that you had failed.