1. There are many nice people in the party.
2. There are many nice persons in the party.
a. Do people and persons mean the same in the above sentences?
b. Are the above sentences in correct structure?
c. There is no plural form for people. Am I right?
d. There is plural form for person. Am I right?
In the, fairly uncommon, sense of 'the people who live in a certain country/region', people can have a plural form.
The peoples of the Middle East must come together.
Persons is used in legal and similar contexts, so it desn't fit for a nice party for me.
What about a dining /coffee set for 6 ... - is persons acceptable in such contexts?
Yes, but people is preferable for the reasons stated above.
Better still is a dining/coffee set for six (people is understood).
Aside from being a social gathering, a party can be "a number of people traveling or working together as a unit, a search party." (Oxford American Dictionary) In this context, "people in the party" would be appropriate.
Thank you very much for all replies from this forum. Sorry, but who should I follow?
All of us.
In answer to your question in post #1 we all seem to agree that people is preferable to persons.