Denshi Jisho — Online Japanese dictionary

減少 げんしょう decrease; reduction; decline
Common word, Noun, Suru verb, No-adjective 

You can also

Look up kanji details for 減少.

Try a Yahoo Jisho search for 減少 .
Try a Goo Jisho search for 減少 .
Try a Google search for 減少 .