题目内容：

不可数名词前的a
《圣经》创世纪第一章第二节：
the earth was a formless void and darkness covered the face of the deep,while a wind from God swept over the face of the waters.
wind from God的备注里又有：Or while the spirit of God or while a mighty wind
请问wind本来是不可数的,为什么a wind from God和a mighty wind中,都用了a?
注：a wind from God,a mighty wind,the spirit of God都是” 神的灵”的意思.