Specifically, a period of ten years, beginning on January 1 of a year ending with a zero when written, and ending at midnight on December 31 of the year nine years later
A 10: 1 increase or decrease of a variable, usually frequency A 20 dB/decade gain roll-off defines a gain change of 20 dB each 10-fold increase or decrease in frequency Note that 6dB/octave is equivalent to 20 dB/decade
A decade is a period of ten years, especially one that begins with a year ending in 0, for example 1980 to 1989. the last decade of the nineteenth century. a period of 10 years (décade, from dekas, from deka )