settlement - when a lot of people move to a place in order to live there, especially in a place where not many people have lived before
That was the definition of settlement that I checked up in a dictionary.
And it also says it’s an uncountable noun.
But I found a sentence example in another dictionary as below:
The British Empire had many settlements.
So it is okay to put “s”?
‘settlement’ has a lot of meanings.
In your second example it is like a village or a town and in this case we have the plural form.
Both are correct depending on context.
Israel has settlements in the West Bank.
Israeli settlement in the West Bank has intensified.
In one case, it is being used as a form the the verb ‘to settle,’ with the ‘-ment’ suffix meaning something like 'the process of doing [whatever the root verb is]. That is, the abstract process by which a territory is settled.
In the other case it is being used as a noun, and can thus take the plural ‘-s’ marker to refer to individual locations where people have their homes.