The inch is a unit of length in the imperial unit system with the symbol in.
There are 12 inches in a foot and 3 feet in a yard. Therefore there are 36 inches in a yard. There are exactly 2.54 centimetres in an inch.
Borrowed from the Latin 'uncia' - the English word 'inch', the origination of the word came from the Old English word for 'ounce' which was related to the Roman phrase for "one twelfth".
The inch is still a commonly used unit in the UK, USA and Canada - and is also still used in the production of electronic equipment, still very evident in the measuring of monitor and screen sizing.
The nanometre is a unit of length and is a multiple of the SI unit metre. It uses the symbol nm.
1 nm is equal to one one-billionth of a metre. (Nano is the prefix for one billionth). It is used to express dimensions on an atomic scale for example a helium atom has a radius of approximately 0.03nm.
The nanometre was previously known as the millimicrometre (or the millimicron).