[Skybydo]

In Wikipedia in the article of "solvent" diethylether is listed as a non-polar solvent. However, my professor draw it like the attached image and said it is polar.
Does it have the two properties?
How should I treat it in SN₁ and SN₂ reactions?

[Dan]

Most organic molecules are polar by definition - they have a dipole moment (ethers included).

In the context of solvents, polar refers to solvents with higher polarity, and non-polar to solvents with lower polarity. It's relative. Diethyl ether is at the lower end of the polarity scale and so is generally considered a "non-polar" solvent - though what we really mean is a low polarity solvent.

This sliding scale situation comes up a lot in chemistry. Another example is when someone asks, "is methanol acidic?". To which the answer can only be, "compared to what?". It's all relative.

[Skybydo]

Ok, it's relative. Thank you!

[msalexanderjohn]

any molecue having atoms of different electronegativity is polar.

[Nosterius]

any molecue having atoms of different electronegativity is polar.

As Dan said, you need a dipole moment to define a molecule as "polar". This definition fails short in that carbon dioxide, for example, has different atoms, but no dipole moment. Same goes for methane, CBr4, ethane, benzene etc...