lucrative adj. 赚钱的，有利可图的

　　词根记忆：lucr+ative赚钱的

　　Burdened by debt, Lydgate abandons his dreams of reforming medicine to take a conventional but lucrative practice in London.

　　advantageous, gainful, profitable, remunerative

　　ludicrous adj. 荒唐可笑的

　　词根记忆：lud+icrous闹着玩的可笑的

　　Although his attempts to appear psychotic were so clumsy as to be almost ludicrous , there is evidence that Ezra Pound was able to avoid standing trial for treason merely by faking symptoms of mental illness.

　　laughable, comic, comical, droll, farcical

　　lugubrious adj. 悲哀的;忧郁的

　　Much of the clowns success may be attributed to the contrast between the lugubrious manner he adopts and the general hilarity that characterizes the circus.

　　melancholy, dolesome, dolorous, lamentable, plaintive

　　luminous adj. 发光的;发亮的;光线亮的;明白易懂的;有光泽的

　　词根记忆：lumin+ous发光的

　　Although supernovas are among the most luminous of cosmic events, these stellar explosions are often hard to detect, either because they are enormously far away or because they are dimmed by intervening dust and gas clouds.