A very high officer of the state in the old Muslim empires — above all the Ottoman Empire, but also in Persia, Egypt, and the Mughal empire in India. The vizier ran the government day to day: he handled money, the army, the courts, and the paperwork, while the sultan or caliph stayed above it all. The most powerful one, the head of all the others, was called the grand vizier, and in the Ottoman Empire he was close to what we would now call a prime minister — he could sign treaties and lead armies, and he kept the sultan's seal. It is a historical word: no country has a vizier today, so you will meet it in history books, in translations of the Arabian Nights, and in films and games set in a fantasy Middle East. Because of those stories, the word has picked up a second flavour in English: the scheming vizier, the clever adviser standing behind the throne, quietly plotting to take it. That is a Western storytelling habit, not history, but it is strong enough that if you say vizier to an English speaker, many of them picture a villain. Two spellings you may see for related words: wazir and vizir. All the same office.