Explores the subject of Chatzi Shiur as it relates to Melachas Shabbos, and how it may differ from the standard rule of "Chatzi Shiur Assur Min Hatorah". In the case of most Issurim, if one performs the forbidden action but with less than the shiur (for example, consuming less than a k'zayis of a forbidden food), he has still transgressed the issur (but will not receive punishment). However, in the case of Melachos Shabbos, it is possible that if one does not complete the Melacha, he has not transgressed the Issur Min Hatorah. The essence of Melacha is that it must be complete - otherwise, it is not really the Melacha at all. We will discuss the machlokes regarding this Sevara, and the numerous halachic applications.