know from

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Related to know from: know from Adam

know someone from someone

to tell the difference between one person and another. I don't knowFred from his twin brother. I know Bill from Bob, but I can't tell most identical twins apart.
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know something from something

to tell the difference between one thing and another. (Often with a negative.) You don't know a smoked herring from a squid! She didn't know a raven from a crow, and who does?
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know from something

to know about something. (Used on the eastern seaboard.) Do you know from thermostats? You don't know from anything!
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