Portugal (UK /?pt?l/; US i/?p?rtl/; Portuguese: Portugal [pu?tua?]), officially the Portuguese Republic (Portuguese: República Portuguesa), is a unitary semi-presidential republic. It is located in South-Western Europe, on the Iberian Peninsula, and it is the westernmost country of mainland Europe, being bordered by the Atlantic Ocean to the west and south and by Spain to the north and east. Aside from continental Portugal, the Portuguese Republic holds sovereignty over the Atlantic archipelagos of Azores and Madeira, which are autonomous regions of Portugal. The country is named after its second largest city, Porto, whose name derives from Latin "Portus" and Celtic "Cale".