I am looking for an idiom/phrase which would mean that someone is trying to explain something to someone who obviously knows how it's done. It would be like a maths student trying to teach/explain to his maths professor in his university how to do calculus - he clearly knows it better than you!

My language has for example "nie ucz ojca dzieci robić" - that translates as "don't teach a father how to make kids" - is there an equivalent in English?

  • There’s preaching to the choir – Jim Nov 16 '17 at 16:49
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    @Jim: Nah. That has an entirely different meaning. – Robusto Nov 16 '17 at 16:50
  • @Robusto - yeah, that’s why I didn’t put it as an answer. It fits marginally with the title. – Jim Nov 16 '17 at 16:51
  • Search the term and you get the idiom: pl.bab.la/slownik/polski-angielski/… – mplungjan Nov 16 '17 at 17:53
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    potrzebujemy SE języku polskiego. – Spencer Nov 16 '17 at 20:03

You don't teach your grandmother how to suck eggs.

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    This is generally more rural/colloquial, but it's what I thought of first. +1 – Robusto Nov 16 '17 at 17:50
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    +1 because it's an exact match in traditional meaning. The only problem with it is that I think a lot of people don't know what it means. I thought it was a straight-up insult until well into adulthood (emphasis on your grandmother sucks eggs, along the lines of your mother wears combat boots) and there have been at least a couple of questions here about "this strange phrase", so it may be best to use it with a cautious eye on your audience. – 1006a Nov 16 '17 at 20:16

A current term is mansplaining. Originally, this meant by a man to a woman, but the Wikipedia article suggests that it can be used more generally.

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  • I first heard the phenomenon discussed byTom and Ray on the NPR "Cartalk" show. I cant recall exactly when but Im guessing about 2000. They used the term MES for Male Explanation Syndrome. – Philip Roe Nov 16 '17 at 19:38
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    +1 The phrase also has a lot of snowclone potential: it can be modified to suit the situation in some obvious way. For the OP's example, perhaps mathsplaining. – 1006a Nov 16 '17 at 19:48
  • Snowcloning is a lot more likely than using "man"splaining in a context other than a man to a woman – Daenyth Nov 16 '17 at 20:02

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