drop down drop off

两者都可表示“掉”、“落”,区别如下：
1.表示从高处往下掉或降,两者有时可互换.如：
The temperature has dropped [fell].气温降低了.
He dropped [fell] from the top of the building.他从屋顶掉了下来.
2.fall 表示“落下”,多指无意识的行为,有自然坠落之意,且通常是不及物动词；drop 既可指无意的行为,即表示“落下”(不及物),也可指有意的行为,即表示“投下”(及物).如：
Rain began to drop [fall].开始下起雨来.
Drop the hammar down to me.把锤子扔下来给我.
He dropped the letter into the mail-box.他把信投入信箱.
Medical supplies are being dropped to the stricken area.目前正将医药用品空投到灾区.