Penal means relating to punishment or the legal system for punishing crimes. A penal code is the set of laws that explains what counts as a crime and what punishment each crime carries. When someone breaks the law, they enter the penal system, which includes courts, jails, and prisons.

You might hear about penal colonies, which were settlements where countries sent convicted criminals as punishment. Britain famously established a penal colony in Australia in the 1700s, sending prisoners there to serve their sentences far from home. The United States used Alcatraz Island in San Francisco Bay as a penal institution, or prison, for dangerous criminals until 1963.

When something is penal, it has to do with how society decides to punish people who break its laws. A penal sentence is the punishment a judge gives to someone convicted of a crime: it might be time in prison, community service, or a fine.

Related words include penalize, which means to punish or put at a disadvantage, and penalty, which is the punishment itself. In sports, a penalty is a disadvantage given to a team or player for breaking the rules.