1. Numbers, general functions and statistical symbols represented by letters, such as straight line L, rectangle ABCD-a1b1c1d1.

2. Variables in mathematics and physics, and functions that change with variables. , representing scalar letter symbols, such as f (x); x= 1

3. symbols of physical quantities, such as v, s, t.

4. concentration symbols in chemistry, such as n, m.

5. Biological scientific names, such as Chl.a, Chlorophyta.

6. Russian letters indicating unit codes, such as cm and Ф (diameter)

7. Common Greek letters? ,? , π

8. Foreign languages, such as French and Latin in the article. Such as: etc. And others.

9. The title of the book quoted in the article, the title of the article, and the name of the ship, such as Titanic.