firm 用作副詞的用法十分有限，通常只能與 stand, hold, stay 等少數(shù)動(dòng)詞連用，且位于動(dòng)詞之后；而firmly 的用法則十分廣泛，且可位于動(dòng)詞之前或之后。如：

Always hold firm to your beliefs. 一定要堅(jiān)守信仰。

They stood firm against the war. 他們堅(jiān)決反對(duì)戰(zhàn)爭。

I firmly believe that it is true. 我堅(jiān)信那是真的。

The fence posts were fixed firmly in the ground. 柵欄的立柱牢牢地固定在地上。

They were firmly convinced that they were the rightful owner of the lands. 他們堅(jiān)決相信他們是土地的合法主人。

【注】hold firmly 通常用于本義，指“緊緊握住”；而 hold firm 則通常用于引申義，指“堅(jiān)持(原則、理想、信仰等)”。