power

In alternating current circuits involving inductive or capacitive loads, the voltage and current waveforms are out of phase with each other by an angle usually designated as φ. In such cases, the voltage x current is called "apparent power," but the real power delivered to the load is V A cos φ. The former is va (or kva); the latter is w (or kw). Also see previous thread.

the short defination of power factor?

Cos φ.

That was already answered in the other thread.

http://www.google.co.uk/url?sa=t&source=web&cd=1&ved=0CB0QFjAA&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPower_factor&ei=uA-TTc_CEJCahQeI78yHDw&usg=AFQjCNGyIDMejR8IGu731B6p5NpmrhJBJQ

http://cr4.globalspec.com/search/sitesearch?do=show&sort=textmatchrank&srch=power%20factor&srchobjs=t%2Cc&fs=12&order=asc

Power factor is the percentage of electricity that's delivered to your house and used effectively, compared to what is wasted. 1.0 power factor means that all the electricity that's being delivered to your home is being used effectively for its purpose. Most homes today have a power factor of 0.77 or less.

Also, Power factor is defined as the cosine of angle between Voltage and current.

Also, Power factor is defined as the ration of active power and apparent power.