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Related to tell on: tell off
tell on (someone or something)
1. To report someone's misdeed or bad behavior to someone in a position of authority. (This person can be specified between "tell" and "on.") We were worried he would tell on us, so we promised him $50 if he kept quiet. Ouch, that hurt! I'm telling Mom on you! The whistleblower was treated as a pariah in the industry for telling on his former employer for evading corporate taxes.
2. To begin to show a negative effect that something is having on one. The lack of sleep from having two young children is really telling on Charles lately. The increasing reliance of consumers on smartphones and tablets has begun to tell on the print newspaper industry.
tell someone on someone
to tattle to someone about someone. I'm going to tell your mother on you! I'll tell the teacher on you!
tell on someone
to report someone's bad behavior; to tattle on someone. If you do that again, I'll tell on you! Please don't tell on me. I'm in enough trouble as it is.
Tattle on, inform on, as in Marjorie said she'd tell on him if he pulled her hair again. This seemingly modern term appeared in a 1539 translation of the Bible (I Samuel 27:11): "David saved neither man nor woman ... for fear (said he) lest they should tell on us."
1. To inform some authority that someone has behaved badly or illegally: The janitor told the teacher on me for writing on the desk. We didn't want to tell on our friends for shoplifting. I promised not to tell on my brother for eating cookies before dinner.
2. To have an effect or impact on someone or something: The stress of working long hours began to tell on the store's owner.