Adjustable means able to be changed or modified to fit different needs or situations. An adjustable wrench can open wider or narrower to grip different sizes of nuts and bolts. An adjustable chair lets you raise or lower the seat to match your height.

When something is adjustable, it's designed with flexibility built in. A baseball cap with an adjustable strap can fit different head sizes. An adjustable lamp can bend to shine light exactly where you need it. A thermostat is adjustable because you can set it to different temperatures.

Adjustable things are useful because one size rarely fits everyone. Think about car seats: they're adjustable so short and tall drivers can both reach the pedals comfortably. Or consider the volume control on headphones, which is adjustable so you can make the music louder or softer depending on the situation.

The opposite of adjustable is fixed or rigid, something that stays exactly the same no matter what. A fixed-height desk might work perfectly for one person but be too tall or too short for another. That's why adjustable furniture, tools, and settings make our lives more comfortable and our work more efficient.