SI unit and micro.nano

Tip: What is a nano or micron?

There are words like nano and micro, which, like words like millimetre (m), kilometre (k) and mega (M), express a number of times or a fraction of the basic unit (technically called the SI prefix, an expression adopted by the SI system of units, the international system of units).
These words are of Greek origin and may be unfamiliar to you.
The exceptions are the millimetre, the centimetre, the kilometre and, since the end of 1992, the word hecto, which is all around us.
（In 1992, the unit of air pressure was changed from the millibar (mbar) to the hectopascal (hPa). It is used in weather forecasting.)

There are a number of different units prefixed by the prefix: metres for length, grams for mass.

The SI prefix is basically replaced by 1,000 times or 1/1000 times. However, 1,000 times is often too large to describe familiar objects, so separate words have been created to describe sizes such as 10 times, 100 times, or 1/10 or 1/100 times. Some of the prefixes are shown in the table below, with examples of their use.
Note that the "exponent" in the table is the "what" in the expression "some power". For example, the number 1000 is the same as the number 10 multiplied three times, which can be written down as three times, but multiplying by 10 is a lot harder. So we write 1000 as 10 multiplied by 10³ (10 to the third power). In this way it is shorter, there is no need to count the digits, and it is easier to calculate between exponents (it is hard to write 100,000 x 100,000,000 while counting zeros). In addition, the exponents can be varied in many ways, such as as minus, fractions or numbers with a decimal point, and their use is fundamental to modern society. The use of logarithms is fundamental to modern society and is also used in the calculation of interest rates.
Logarithms are introduced in the section on superfine grinding.

1. Smaller prefixes

2. The larger maller prefixes

Billion

つまりミリメートル（mm）という単位はメートル（m）の千分の一であることを表し、ミリグラム（mg）はグラム（g）の千分の一であることを表しています。
同様にマイクロメートル（記号ではμm）は、ミリメートルの千分の一の大きさであることを、ナノメートル（記号ではnm）はμmの千分の一の大きさであることを表しています。

Appendix: What is a "micron"?

Before the SI system of units was used, the micrometer was called a micron (written in µ).
Even today it is still customary to say micron, as it is too long and cumbersome to write or say micrometer.
It is not an accepted expression in international standards and is therefore not used in documents.

This term is also widely used as submicron. In this case, it is one digit smaller than a micron, which in the SI system of units means a size between 100 nm and 1 µm.