to speak critically about someone; to say a person’s name without giving the proper respect to him or his ideals
—Professor Smith was a great teacher. You are taking his name in vain when you say that he didn’t care about his students.

The third of the Ten Commandments that God gave to the Israelites on Mt. Sinai is

You shall not take the name of the Lord your God in vain, for the Lord will not hold guiltless anyone who takes his name in vain. (Exodus 20:7)

A more modern way of saying “take God’s name in vain” is “misuse God’s name.” This can include using his name to swear that something is true when it isn’t. Another way to misuse God’s name is to speak it in a disrespectful or thoughtless way. An example is when someone says, “God,” to show surprise, anger, disgust, etc. Probably the most common example of this today is Oh my God, which is used to take the place of phrases such as Uh oh, Oh no, or Wow. It is also written and spoken as the abbreviation OMG.

O my God is used in the Bible as a way of addressing God in prayer. For example, the prophet Ezra, with great respect, prayed,

O my God, I am ashamed and embarrassed to lift my face to you, my God! For our iniquities have climbed higher than our heads, and our guilt extends to the heavens. (Ezra 9:6)

Some people try to avoid using God as an exclamations by replacing it with such words as gosh, goodness, or golly. But some find even these substitute words offensive, while others think they sound childish or old fashioned.