Achaia is a region located in the northern part of Peloponnese in Greece, which was known as one of the major regions of the ancient Greek world. The word Achaia has been used with different spellings over the years, including Akhaia, Akhaie, and Akhaika. The most commonly used synonym for Achaia is the term Peloponnese, which refers to the peninsula where Achaia is located. Other synonyms for Achaia include Arcadia, Argolis, Corinthia, and Laconia, which are also regions located within the Peloponnese. Achaia is often associated with the history of ancient Greece, and its name remains prominent in modern-day Greece.