To legalize something means to make it lawful or permitted by changing the rules that govern it. When a government legalizes an activity, it removes laws that previously made that activity illegal or restricted.

For example, in many places, riding a bicycle on sidewalks is illegal, but a city council might legalize sidewalk cycling in certain neighborhoods by passing a new ordinance. When a state legalizes a medical treatment, doctors can prescribe it without breaking the law. Immigration laws can legalize a person's status in a country, allowing them to live and work there officially.

The word often appears in debates about what society should permit. Some argue that legalizing certain activities makes them safer because they can be regulated and monitored. Others worry that legalization sends a message that something is acceptable, even when perhaps it shouldn't be.

Legalization is the noun form: “The legalization of skateboarding in the plaza took three years of petitions and town meetings.” Notice that legalizing something doesn't necessarily mean encouraging it. It simply means removing legal penalties and allowing people to make their own choices within a framework of rules.