The word repertoire is derived from the French répertoire, and means the collection of music composed for a given instrument, voice, or ensemble. It is mostly used in connection with classical music.
One may use the term to include transcriptions, reductions, and adaptations, or restrict it to music originally written for the instrument.
The piano repertoire is one of the largest and most diverse, including (inheriting) much of the keyboard repertoire originally written for older instruments such as organ, harpsichord, clavichord, and spinet, and also piano reductions of orchestral works.
There is some overlap between the flute, oboe, and violin repertoire in chamber music. Many composers have written trios or quartets with the choice of two of them for the first part.