Inflexible means unable or unwilling to change, bend, or adapt. When something is inflexible, it stays rigid no matter what happens around it.

A plastic ruler is flexible because you can bend it and it springs back. But a wooden ruler is inflexible: try to bend it and it will snap instead of curving. Metal can be inflexible too: a steel rod won't bend in your hands no matter how hard you try.

People can be inflexible in their thinking or behavior. An inflexible teacher might refuse to accept late homework even when a student has a good reason, sticking to the rule no matter what. An inflexible schedule has no room for adjustments: if you planned every minute of your Saturday and won't change anything when your friend invites you to the park, you're being inflexible.

Being inflexible isn't always bad. Sometimes you need inflexible rules, like always wearing a helmet when biking. But inflexibility can also cause problems. When you face unexpected situations, inflexible thinking makes it hard to find solutions. A good problem solver stays somewhat flexible, able to adjust their approach when the first plan doesn't work.

The opposite of inflexible is flexible: bendable, adaptable, and willing to change when circumstances call for it.