using iMac memory in a Mac mini

The Late 2014 Mac Mini's RAM is integrated into the logic board and not upgradable.

see > https://support.apple.com/en-us/HT205041

If you happen to have a Late 2012 Mac Mini?

It has 1600MHz DDR3 PC4-12800RAM and may or may not work using 1867MHz DDR3 PC3-14900 RAM from say a Late 2015 iMac.

Also all Mac's are very RAN sensitive and with not work using budget or PC RAM even if it is the same spec.

With that said: I concur with D.I.Johnson and suggest that you visit OWC or Crucial and use the correct spec's for your Mac Mini if it is upgradable.

It's likely that the RAM modules from your iMac are NOT compatible with the mini.

I would suggest you check availability and compatibility of RAM at OWC/Macsales.

Most veterans here will also recommend you only use memory from OWC or Crucial.

You're welcome.