Why does 减弱 (lit. "reduce weak") mean "to weaken"?
肥 in 减肥 is a noun; 弱 in 减弱 is an adjective
减肥 = 减(少)肥(胖) = reduce obesity
减弱 = 减(低)(變)弱  decrease and weaken
Example:
&quot;颱風减弱&quot; = &quot;颱風(威力)减(低)(變)弱&quot; = &quot;Typhoon (power) decreases and weakens&quot;
The power decreased and the typhoon became weaker