Estada vs. estadia
The difference between estada and estadia refers to a traditional grammatical rule regarding who or what is staying in a place. Historically, the rule dictates a specific usage for people versus vehicles. However, in modern usage, particularly in Brazil, this distinction has become blurred, and one term is frequently used for both contexts.
Estada
B2Strictly speaking, estada refers to the act of a person staying or residing temporarily in a place. It represents the permanence or sojourn of people. In Portugal and in formal Brazilian Portuguese, this is the preferred term when talking about human beings.
A nossa estada no Brasil foi inesquecível.
(Our stay in Brazil was unforgettable.)
Durante a sua estada, o presidente visitou vários museus.
(During his stay, the president visited several museums.)
Desejo que a vossa estada seja muito agradável.
(I wish that your stay is very pleasant.)
Ela prolongou a sua estada em Lisboa por motivos de trabalho.
(She extended her stay in Lisbon for work reasons.)
Estadia
B1Traditionally, estadia refers to the time a vehicle (such as a ship in a port, a plane at an airport, or a car in a parking lot) remains grounded or docked, including the fee paid for that time. However, in widespread modern usage (especially in Brazil and increasingly in the tourism industry in Portugal), estadia is commonly used to refer to a person's stay in a hotel or vacation rental.
O capitão pagou as taxas referentes à estadia do navio no porto.
(The captain paid the fees regarding the ship's stay at the port.)
O preço da estadia no estacionamento do aeroporto é muito caro.
(The price of the stay at the airport parking lot is very expensive.)
O hotel exige o pagamento da estadia no momento do check-in.
(The hotel requires payment for the stay at the moment of check-in.)
Reservamos uma estadia de cinco dias no resort.
(We booked a five-day stay at the resort.)
Summary
According to traditional grammar, you should use estada for people and estadia for vehicles or ships. However, usage has evolved significantly. In Brazil, estadia is now the standard term for hotel stays and tourism, and using estada can sound overly formal or literary to casual speakers. In Portugal, the distinction is respected more often, but estadia is also widely accepted in the context of hospitality and tourism.