To become something different.
The tadpole changed into a frog. Stock prices are constantly changing.
To make something into something else.
The fairy changed the frog into a prince. I had to change the wording of the ad so it would fit.
To replace.
Ask the janitor to come and change the lightbulb. After a brisk walk, I washed up and changed my shirt.
To replace one's clothing.
You can't go into the dressing room while she's changing. The clowns changed into their costumes before the circus started.
To replace the clothing of (the one wearing it).
It's your turn to change the baby.
To transfer to another vehicle (train, bus, etc.)
To exchange.
To change hand while riding (a horse).
to change a horse