Behaviour of electrical elements

Mebbe, Koy, it's where powers are entailed, like "squared," "cubed," etc
Lousy answer; help, somebody

Where something is nonlinear for instance it could be building upon itself
Forgive, achu, my wild guess, and gezundheit

As an electronics hobbyist, I can say that in practical circuits, most of the nonlinear behavior has to do with semiconductors-diodes and transistors and such. The so-called pn junction, both singly as in a diode, and a compound arrangement such as a transistor, (pnp or npn), are nonlinear, and from this we can get amplification, compression and expansion of the signal, and a whole host of effects that comprise modern electronics.

Here's a quick overview of diodes, transistors, and FET, (field effect transistors). There are other semiconductor devices as well.
https://www.renesas.com/en-us/support/technical-resources/engineer-school/electronic-circuits-02-diodes-transistors-fets.html

Here's a chart of a nonlinear element, the diode. Look at the forward voltage. From 0 to 0.7 Volts, (silicon diode), no voltage is passed by the diode. But over 0.7 Volts, voltage is passed. Compare that behavior with a transistor, which will pass voltage as it is applied to it.

This video explains it better. The narrator has a little bit of an accent, but his points are clearly made and it's worth listening closely to him. The video is only 2 minutes long, so it's worth listening to again if you missed anything.

Thanks Blick for amplifying my feeble attempt. I too was an electronics hobbyist but I can't help thinking there's a deeper meaning to nonlinearity; something much deeper than me

Well, in really advanced physics, they examine every single nonlinearity, no matter how infinitessimally small, and frequently make discoveries from those. These discoveries usually are announced by a team of scientists using an atom smasher five miles long and staffed by a multi-story building full of researchers and equipment.

But the OP just wanted the definition needed by students beginning to study electronics, so that's what I gave him or her. I wouldn't be much good working on one of those research teams with the five mile long atom smashers anyway,

Yes, but no, Blick, your posting was most excellent