The start is the beginning of something, when it starts to move or work gets underway. The people in the picture are starting a race.
The opposite of start is stop, finish or end. A similar word to start is begin.
You stop doing something when you don't do it anymore. You can also stop someone else from doing something, or stop an action and end it early. For example, "she brought a stop to the daily meetings".
The opposite of stop is go or start.
