Define the unit newton.

Hint
Newton is the SI unit of force. We will see what an SI unit is, the definition of Newton and how to use it in the below discussion.

Complete step by step answer
The SI base units are the standard units of measurement. It is defined by the International System of Units (SI). We should write the names and symbols of SI base units in lowercase. There are some exceptions, the symbols which are named after a person are written with an initial capital letter.
For example, the kilogram has the symbol Kg, but the kelvin has symbol K, because it is named after Lord Kelvin. Newton is also one of the SI units. It is the unit of force. Force is defined as the product of mass and acceleration. The unit of force Newton is named after Sir Isaac Newton in recognition of his work on classical mechanics, specifically for the second law of motion. The force needed to accelerate one kilogram of mass at the rate of one metre per second squared in the direction of the applied force is defined as one Newton.
As we saw earlier in the rules we should write the unit newton in capital letter as “N” since it is named after scientist Isaac Newton. Only the unit N follows this rule; if we write N in full form as Newton we should write it in lowercase until we write it as the first word of the letter. The full form of the unit of force follows the common rules of punctuation as other words.

Note
We know that force is defined as the product of mass and acceleration, so the unit of force can also be written as kg $m/s^2$ since the unit of mass is kilogram (Kg) and the unit of acceleration is $m/s^2$.