If in my essay I mention a town named Greensea for the first time, what's the right way for me to put it?:
... and then he moved to a town of Greensea
... and then he moved to the town of Greensea
... and then he moved to Greensea town
... and then he moved to town Greensea
How about:
...and then he moved to Greensea.
There is no absolute reason to mention that it is a town. Most readers will pick up on that. Especially if you make it clear in further description as your story goes on, or whatnot. But this site is not for writing advice, and even this answer is an opinion.
Other than that, the most common way to put it is probably:
...and then he moved to the town of Greensea.
with
...and then he moved to Greensea town.
being used in rare occasions.
EDIT TO ADD: This whole notion of Use the indefinite article when you mention something for the first time is an example of a grammar "rule" gone mad. It is not even a rule. It is a writing guideline But even then, it does not apply to towns and cities. Also, it is also true that at least 2 out of 3 "first mentions" of any noun are with the, the most commonly used word in English. Just read anything in English. (Sorry if you were not thinking of that rule, but it comes up over and over in questions about article usage.)
The second is the correct one, as an alternative to using the town's name by itself. While not as common, the lengthier construction is not at all unknown. For example, there is the traditional Christmas song, "O Little Town of Bethlehem," or just do a search on "the city of" or "the town of" (with quotation marks included).
The third may be a rare alternative, and it may be exclusive to Ireland, possibly even Irish song lyrics. See, for example, Red Hill Mining Town and "Moneygall town" from There's no one as Irish as Barack O'Bama.
How much you say about anyone or anything will depend on how much your listener(s) or reader(s) know, or how much you reasonably expect them to know. I can say 'I live in Sydney, Australia', and expect that most people reading this will know about Australia and Sydney. I can say 'I live in Australia's biggest city, Sydney', but probably don't have to.
On the other hand, if I say 'I was born in Sea Lake, Australia', it might be helpful to add something like, ', which is a very small country town in northern Victoria'. (Even most Australians don't know where it is!)
