What are buyers and sellers (or customers and suppliers)

I'm programming a simple software to manage products, buyers/sellers and sales/purchases orders.

A product is simply a product, but what is the english word that refers to both the categories of buyers and sellers (or customers and suppliers)?

I just cannot find the correct term (if it exists), not even in my own language.

Some options I thought would be: ThirdParty, Person, Company. And finally, given the correct word, when I want to state if the ThirdParty is a buyer or a seller, what is it? A type?

I hope my question is clear and pertinent to english.stackexchange. Thank you.

Solution 1:

I usually refer to them as "the parties". That's how they are often mentioned in legal contracts.

Depending on your application, you could call them "traders" or even "merchants".

If you are building a platform where some people buy what others sell, you could call them just "users".