零 is a phono-semantic compound consisting of the semantic component 雨 "Rain" (pinyin: yǔ) and the phonetic component 令 “Order, To Make" (pinying: lìng). Some sources believe that the original meaning of 零 was “Drizzle”.
Though 零 is considered the proper written form for the number "Zero", for certain purposes the alternative written form “〇” is more commonly used as an informal way to represent “Zero”. "〇" is not considered a standard Chinese character, since Chinese characters do not contain ovals or circles.