1. I often go skiing with my friends on weekends.
2. I often go skiing with my friends weekends.
3. I often go skiing with my friends on the weekends.
4. I often go skiing with my friends on the weekend.
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Are they all grammatical? Would you let me know incorrect expressions?
You don't need to answer it?.There was a problem. I posted the qeustion, but I could not find the quetion after I clicked Current Questions. So I posted this question again. ..Later I pressed the refresh butten. Then I could see the posted questions.
SraJMcGin is right. All the sentences are good except for #2. It isn't incorrect; it just isn't used very often.
Out of the four sentences you provided, three of them are grammatically correct and one of them is incorrect. Let's go through them one by one:
1. "I often go skiing with my friends on weekends." - This sentence is grammatically correct. It indicates that you frequently go skiing with your friends, specifically on weekends.
2. "I often go skiing with my friends weekends." - This sentence is not grammatically correct. It is missing the preposition "on" before "weekends". The correct version should be: "I often go skiing with my friends on weekends."
3. "I often go skiing with my friends on the weekends." - This sentence is grammatically correct. It is similar to the first sentence, but specifies that you go skiing with your friends specifically "on the weekends".
4. "I often go skiing with my friends on the weekend." - This sentence is also grammatically correct. It implies that you go skiing with your friends on a specific weekend, rather than every weekend.
So, the only incorrect expression is sentence number 2. Remember to include the preposition "on" before "weekends" when indicating the specific time you go skiing.