"The microwave oven is faster than the kitchen stove."
Translation:Cuptorul cu microunde este mai rapid ca aragazul.
These words cannot be used interchangeable. For equality comparison it should be used "ca", "ca și", "cât" or "cât și". For inequality comparison, both can be used as long as it does not follow another sentence after these words. Otherwise, only "decât" is correct.
- El este mai mare decât/ca mine.
- El este mai mare decât am crezut.
However, in spoken Romanian you will hear a lot "decât" for equality comparison, but try to do not use it, because it can lead to a bad habit. (trust me, it is really hard to get rid of it) :)