early
Happening before the usual or expected time.
Early means happening near the beginning of a period of time, or before the expected or usual moment. If you arrive at school early, you get there before most other students and before the bell rings. If you wake up early on Saturday, you're awake while others are still sleeping.
The word works across different timescales. The early pages of a book are near the front. The early months of the year are January and February. Early humans lived thousands of years ago, near the beginning of human history. An early train is one that departs before later ones.
Early often suggests an advantage. Students who finish their homework early have more free time later. Scientists who identify a problem early have more time to solve it. Farmers who plant early in spring give their crops a longer growing season. Getting somewhere early means you won't be rushed or late.
The opposite of early is late. Notice how this pairing works: if you're early for the movie, you'll get good seats, but if you're late, you might miss the beginning entirely.