A period of ten years , particularly such a period beginning with a year ending in 0 and ending with a year ending in 9.

decadence.

In a decadent manner.

Characterized by moral or cultural decline. / Luxuriously self-indulgent.

A person affected by moral decay.

A state of moral or artistic decline or deterioration; decay / The quality of being luxuriously self-indulgent.

plural of decade.

plural of decadent

plural of decadence

plural of decadeful