Informally means in a casual, relaxed way rather than following strict rules or official procedures. When you dress informally, you might wear jeans and a T-shirt instead of a suit or dress. When you speak informally to someone, you use everyday language instead of careful, proper speech.

Think about the difference between writing an email to your principal versus texting a friend. The principal's email would be formal: “Dear Dr. Martinez, I am writing to request permission...” Your friend's text would be informal: “Hey, can I come over?” Both communicate, but the informal version skips the ceremony and gets straight to the point.

People act more informally around friends and family than around strangers or authority figures. You might address your teacher as “Mrs. Chen” formally but call your neighbor “Sarah” informally. At an informal gathering like a backyard barbecue, people relax and chat freely. At a formal event like a wedding ceremony, everyone follows more careful rules about how to behave.

The opposite of informally is formally. Many situations fall somewhere in between: not super casual but not strictly formal either. Learning when to be informal and when to be more formal is an important social skill.