Stay and stay they represent the dynamism through which the language passes through – since, according to the use recommended by the speakers of a given word, it is incorporated until it becomes dictionary.
Thus, traditionally, we have that "stay" refers to the length of time a ship remains in the port without the payment of any fee for such, or simply the length of stay in that place. So, we say perfectly that:
the stay of Knock Nevis at the port of Santos it took two days.
“Stay”, in turn, refers to the act of being, staying, in a given place. In this way, we can conveniently state:
During my stay in Florianópolis, I got to know the various attractions offered by the city.
However, given the dynamic character highlighted above, the word "stay", even for reasons related to euphony (pleasant sound), started to assume the same semantic meanings attributed to "stay". Therefore, meaning the permanence of people, animals, vehicles, among others, in a certain place. This position is portrayed by at least two Brazilian dictionaries – Houaiss and Francisco Borba.
Given this reality, it doesn't matter whether we use one way or another, as well as the following examples present us:
That international singer's stay on Brazilian soil was short.
Your stay in this enclosure will be for a few days.
The company will pay for the employees' stay during the training course.
By Vânia Duarte
Graduated in Letters
Brazil School Team
Source: Brazil School - https://brasilescola.uol.com.br/gramatica/estadia-ou-estada.htm