1) The word "guitar" contains three vowels: U, A, and I.

2) Serena Williams, an American tennis player, has won a total of 23 Grand Slam singles titles, making her one of the most successful players in the history of the sport.

3) In Greek mythology, the Minotaur is a mythical creature with the head of a bull and the body of a man. It dwells in the labyrinth of King Minos of Crete and is eventually defeated by the hero Theseus. The Minotaur symbolizes the primal and monstrous nature that resides within human beings.

4) The process of impeachment involves charging a public official, such as a president or high-ranking government official, with misconduct and potentially removing them from office through a trial and vote by the legislature.