period
"Period" is a very useful English word with several common meanings. It can refer to a length of time, a punctuation mark, a stage in history, and more. Here are the most important senses you'll encounter.
A period can refer to a specific chapter or era in history — a time that is remembered for particular events, styles, or ideas. Historians use this word a lot.
history and academia · Modern, widely used
A period also refers to menstruation — the monthly cycle that women and girls experience. This is a completely normal, medical term and is not rude or impolite to use.
health and medicine · Modern, widely used