How is 1 ohm specified?

First of all, you have to understand ohm's law:

Resistance (1ω)= voltage (1V)/ current (1A).

And why not: resistance (1ω)= current (1A)/ voltage (1V)?

You have to understand the concept of "resistance", which means "obstruction". Physically speaking, resistance refers to the obstruction of current. The greater the resistance, the greater the obstruction to the current, and the harder it is for the current to flow, so the smaller the current is. Mathematically, the greater the resistance, the smaller the current required, so the resistance is inversely proportional to the current. So it must be:

Current (1A)= voltage (1V)/ resistance (1ω).

If you do as you say: resistance (1ω)= current (1A)/ voltage (1V), you will deduce that,

Current (1A)= resistance (1ω) x voltage (1V).

Is the question coming? You find that the greater the resistance, the greater the current. Can't call it "resistance". Can only be called "conductance", which is how you define yourself in electricity.

Conductivity (1G)= current (1A)/ voltage (1V).

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