Is lying by omission a lie?

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My hubby and I do not keep secrets, or at least we do not purposely.We were talking about a friend who has a wife that has been complaining because he started a new job. His new job starts later then his old one , therefore, he gets home later. Well, the other day he called my husband and asked if he could meet him for a beer after work because he was leaving work early. My husband did, and he was back within an hour and a half. I asked my husband why was he home so soon and he said because our friend has to get home by 6:30 so his wife would not know he went out. This started our conversation on whether lying by omission is a real lie or not. If someone gave you only part of the truth and kept the rest from you knowing the whole scenerio, do you think that person lied to you?