What's the Difference Between a Digital Piano and a Keyboard?

Yamaha Clavinovas
come in Upright or
Grand Digital Pianos

Clavinova = Yamaha's premier line of upright and grand digital pianos

Compact Digital Piano = see Portable Digital Piano

Digital Piano = not a piano (no strings, no need to tune, completely digital, plugs in); 88 keys; it's purpose is to serve as a piano replacement; weighted action similar to that of a high-quality piano; usually offers minimal sounds or "bells and whistles" although a digital piano can be combined with a keyboard

A Keyboard is identified by 76 or
less non-weighted keys and
lots of non-piano sounds & extras

Grand Digital Piano = a digital piano contained in a cabinet made to look similar to a baby grand piano; comes with piano bench, three pedals and adjustable lid; not portable (may require piano movers to safely transport); biggest speakers and therefore best/most realistic sound of the digital pianos

Keyboard = referring to a non-weighted action keyboard, usually 76 keys or less; it's purpose is not to replace a piano, but to offer other features such as sounds, beats, demos, etc.

A Portable Digital Piano may
sacrifice a little in sound and
touch, but it can be an affordable,
compact alternative

Piano = referring to an acoustic piano; has strings, no plug; requires tuning

Portable Digital Piano = also known as Compact Digital Piano; a digital piano that is not designed to look exactly like a piano, but is generally made to look more sophisticated than a keyboard or synthesizer; may or may not come with stand, bench or pedal(s); made to be portable; small speakers mean a sacrifice in quality and realism of sound; light-weight  structure often results in a sacrifice in key weight as well (keys are weighted but may feel "cheaper" than the other types of digital pianos)

The Stage Digital Piano may not
look great in your living room, but
it holds its own as a piano replace-
ment as well as adding lots of
advanced options and features

Stage Digital Piano = a hybrid model with the internal features of a digital piano and a sophisticated keyboard or synthesizer; not designed to look like a piano; heavy, but designed to be portable; usually does not include internal speakers meaning it creates no sound on its own, but must be plugged into an amplifier or PA system to be heard; does not come with stand, bench or pedals (must be purchased separately)--so the sound can be as good or as wimpy as the speakers it is connected to

An Upright Digital Piano has a
piano-like cabinet, closable lid,
3 pedals and a piano bench included

Synthesizer = referring to a keyboard that is specifically designed with creation of new sounds in mind; has 100s or 1,000s or sounds programmed

Upright Digital Piano = a digital piano contained in a cabinet made to look similar to an upright piano; comes with piano bench and three pedals; able to be moved by two able adults, but not designed to be portable; bigger speakers and therefore better/more realistic sound than a portable digital piano