What is the unit of electrical resistance?

The story behind the answer

Ohm (symbol Ω) is the SI unit of electrical resistance. By Ohm’s law (V = I × R), resistance equals voltage divided by current; so 1 ohm is the resistance that allows 1 ampere of current to flow when 1 volt is applied.

Named after physicist Georg Simon Ohm, resistance measures how strongly a material opposes the flow of electric charge. To avoid mix-ups: Joule measures energy, Tesla measures magnetic flux density, and “mho” (ohm spelled backward) is the old name for conductance—the inverse of resistance—now called the siemens (S). Memory tip: “O is for Oppose—Ohm opposes current,” and “mho” being “ohm” backward reminds you conductance is the opposite of resistance.