To begin means to start something or to take the first step in doing, making, or experiencing something. When you begin reading a book, you open to the first page. When a race begins, runners take off from the starting line. When you begin learning piano, you practice your first simple scales.

The word captures that moment of starting: the beginning of summer vacation, the beginning of a friendship, the beginning of a difficult project. Sometimes beginning is the hardest part because you're facing something new or challenging. Other times it's exciting, like beginning an adventure or beginning to understand a concept that confused you before.

Begin and start mean almost exactly the same thing, though begin sounds slightly more formal. You might say “Let's start the movie” but “Let us begin the ceremony.” The word begun is the past participle: “We had already begun to eat when she arrived.”