ADV

politely
absolutely
I absolutely decline to discuss my dealings with him or anyone

ADV

considerably, dramatically, drastically, markedly, sharply, significantly, steeply
The economy has declined sharply in recent years
a little, slightly
fast, rapidly
The market for these products is declining fast
steadily
gradually, slowly
further

PREP

by
Profits declined by 6% this year
from, to
The number of full-time staff has declined from 300 to just 50

PHRASES

decline in importance/numbers/size
This section of the market has slowly declined in importance