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 weekends.

Are they all grammatical?
Would you let me know incorrect expressions?

Thank you for using the Jiskha Homework Help Forum. Having read the later posts, #4 is "weekend" singular, right? The only one that doesn't seem quite as good is #2.

Out of the four provided sentences, three of them are grammatically correct, and one of them contains an incorrect expression. Here's a breakdown of each sentence:

1. I often go skiing with my friends on weekends.

This sentence is grammatically correct. It is common to use "on" to indicate a specific day or time when referring to recurring events. In this case, "on weekends" refers to the regular occurrence of going skiing with friends.

2. I often go skiing with my friends weekends.

This sentence contains an incorrect expression. It lacks the word "on" before "weekends." The preposition "on" is required to specify that the activity of going skiing with friends happens during the weekends. Thus, the correct version of this sentence would 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 includes the preposition "on" before "the weekends," indicating that the activity takes place during specific weekends.

4. I often go skiing with my friends on the weekends.

This sentence is grammatically correct. It is similar to sentence 3, with the addition of the article "the" before "weekends." While it is not necessary to include the article "the," it is also not incorrect to do so. Both versions are acceptable.

So, to summarize, sentence 2 is the only one with an incorrect expression. The correct sentence would be: "I often go skiing with my friends on weekends."