That popular phrase is used to refer to a situation in which one person's negative demeanor or bad behavior can affect a whole group of people, influencing them to have a similar negative attitude or to engage in the same bad behavior.
The phrase comes from the idea that one rotten apple amongst a bunch of other apples can cause the others to go bad. But is that true? Can one bad apple really spoil the whole bunch? And if it can, why does it do that?
No one knows for sure how or when this phrase got its start. It does have some basis in science, though. When apples begin to decay, they emit gases. If the rotting apple is mixed in with a group of other apples, the good apples can absorb these gases and begin to rot, too.
Of course, we don't always buy apples in big bunches today. Apples are readily available at the supermarket, so many people just buy a few at a time as they need them. If you ever do buy a bunch of apples, though, you might see this phrase in action if you don't eat them right away and one begins to rot.
So it's easy to see how people's real life experiences with apples in the distant past could have given rise to this common phrase we still use today. If you've ever seen how one person's negative attitude or bad behavior can influence a whole group to think or act in the same way, then you can see why the phrase became so popular to describe people and situations, too. An example is when a bully spreads negative information and influences others to be mean and behave badly. In that case, one person certainly can spoil the bunch!
You may feel these influences from time to time at school or in other social situations. Sometimes it's referred to as peer pressure. This simply means the pressure you might sometimes feel when those who are similar to you — your peers — think or do certain things.
It can be hard to stand up for yourself and think or do the right thing when others are thinking or doing the opposite. How hard can it be? It can be difficult if even just one influential individual has a negative attitude or behaves badly.
But one bad apple doesn't have to ruin the whole bunch. You can think for yourself and you can do what is right — regardless of what others are doing. Stay true to yourself and stand up for your beliefs!