1. He helped to organize the party.

2. He helped to arrange the party.
3. He helped to prepare the party.
4. He helped to prepare for the party.
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Can we use all the expressions? Which ones are commonly used?

5. He helped organize the party.
6. He helped me to organize the party.
7. He helped me organize the party.
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Do you use #5 without 'the' before 'organize'?
No problem in using?

#1,2,3, & 4 - "to" is unnecessary. "He helped organize the party." "He helped arrange..", etc. Otherwise they are all used and mean the same, more or less. In #6, again, "to" is unnecessary. They all are acceptable. All can be used. To organize the party might imply help with deciding whom to invite, issuing invitations, etc. Preparing for the party might imply setting the table, cleaning the house, cooking foodn and such, but both may include organizational and the practical tasks in getting ready for a party.

1. Yes, all the expressions you provided can be used to convey the same meaning, which is that he assisted in getting things ready for the party.

2. Out of the options you provided, #1, #2, and #4 are commonly used and grammatically correct. They all convey the idea that he played a role in organizing and preparing for the party.

3. While #3 is grammatically correct, it is not as commonly used as the others. "Preparing the party" can imply that he physically set up the party, such as arranging decorations and food, rather than focusing on the logistical aspects of organizing the event.

4. In regards to #5, "He helped organize the party" is a commonly used expression without the article "the" before "organize." It is a shortened, more concise form of the phrase. However, both "He helped organize the party" and "He helped to organize the party" are grammatically correct and widely understood.

5. Yes, there is no problem using #5 without the article "the" before "organize." The sentence "He helped organize the party" is a valid and frequently used construction in English.