Yeah
They both sound like a piano.
synthesizer/electric piano.
Yes. An Electric Piano; there is such a thing.
A Yamaha electric piano can be purchased at music stores. They probably wouldn't be available in electronics stores, but one could look on Amazon or eBay.
A keyboard is electric A piano is non electric
An electric piano is played the same way a regular piano is played only you do not have to use as much pressure when hitting the keys. You have more options for creating different sounds with an electric piano.
Depends how high and hard you crank up the electric piano. Also depends on what kind of pianos they are. But acoustically a normal piano will have the same volume if not more than an electric one.
an electric pianist
A piano has a keyboard. But is doesn't look like the keyboard on your computer.
Electric keyboard usually refers to the keyboard of an electric piano. "Keyboard" is a generic word that can refer to an electric piano, an acoustic piano, a typerwriter keyboard, a computer keyboard, etc.
The electric piano evolved from the early 1920s. The Neo Bechstein was an early model. Like the electric guitar, the electric piano uses a coil pickup to amplify (and subsequently shape) the sound of actual strings or tines being played. Harold Rhodes' version of the instrument became hugely popular from the 1950s-1970s.