卜辭「亦」字的用法歷來有三種說法，一是假為「夜」說；二是解為「再」、「又」說；三是釋作「也」。其中以後二說的影響最大，學者多從之。直到近來有學者重申「亦」假為「夜」之說，認為部分殷卜辭的「亦」仍應讀為「夜」。可見目前學界對於殷卜辭「亦」字的用法仍存在爭議。本文透過重新整理檢視卜辭的亦字句，認為卜辭「亦」字用法主要作為副詞使用，有的用為範圍副詞「也」；有的用作頻率副詞「再」、「又」。既可以用來表示兩件事的類同關係，也可以用來表示一件事或同性質事件的重複與繼續。殷卜辭目前尚未見一條完整而確切無疑可以讀為「夜」的「亦」字辭例。卜辭「亦」字是否有假為「夜」的用法，則仍需更多的證據證明。

There are three theories about the meaning of the character “Yi” 亦 in the Shang Oracle-bone Inscriptions ： 1. “Yie” 夜（night) ； 2. ‘ “Zai” 再 (again) and ‘ “You” 又（again) ； 3. ‘ “Yie” 也（too). The latter two theories have been more influential and widely accepted. But recently, some researchers are pointing out that the character “Yi” 亦 should be read as “Yie” 夜( night) .
No definitive conclusion has been reached on the meaning of the character “Yi” 亦.This study aims to re-analyze the dictions of “Yi” 亦 in the Shang Oracle-bone Inscriptions. The character was mainly used as adverbs; sometimes as the range adverb “Yie”（也），while other instances as the frequency adverb “Zai” 再（again) and “You” 又（again). However, there is little evidence of it being used as the time word “Yie” 夜( night) .