Social influence means someone affecting the emotions, opinions, or behaviours of others. It can be either planned for a purpose, or be an unplanned result of other events.

The adjective influential means "having much influence", so influential people or things have the power to change other people or things in some way. This word is often used to describe famous people. For example, Mahatma Gandhi was a very influential person, because the things he did and said changed many peoples lives, and many people believe he has even influenced the world. Kings, clergy and celebrities are also among the influential, as people pay attention to what they say or do.