An instrument is a concrete or abstract tool intended for a purpose other than mechanical work, in particular a refined one.
Musical instruments are devices designed to produce music, frequently by plucking or striking a string or bell or drum surface, or by forcing air to resonate (see wind instruments).
... can mean the following:
dB is the abbreviation for Decibel; see Bel
DB is a French automobile maker; see DB (car)
DB is the abbreviation for Deutsche Bahn, the ...