loud, loudly

loud作副词时和loudly是同义词。不过二者还是有细微的区别：loud是指声音的音量大，一般用于动词后，尤其在非正式场合，经常连用的动词有talk, speak, shout, laugh等；而loudly有“喧闹”的意思，多含贬义。

试比较：

Don't speak so loud, please.请不要这么大声地说话。

She complained loudly of having been badly duped.她吵吵囔囔地埋怨起来，大呼上当。