The piano, formerly also pianoforte or, more rarely, fortepiano, today piano for short, is a musical instrument invented towards the end of the 17th century, in which small hammers are struck against strings by means of a special mechanism at the press of a button. In terms of operation, the piano is therefore a keyboard instrument, in terms of the type of excitation a percussion instrument and in terms of the vibrating medium a string instrument. The modern main forms of the piano are the grand piano (English grand piano) and the pianino (English upright piano).