In mathematics, "ch" is usually the abbreviation of a function, namely "hyperbolic cosine function". Its expression is ch (x) = (e x+e (-x))/2, where e is the base of natural logarithm. This function is widely used in many fields of mathematics. For example, in physics, hyperbolic cosine function is used to describe the motion process similar to elastic collision. In the engineering field, it is often used as a calculation tool for power factors of current and voltage in electronic circuit design.

Besides hyperbolic cosine function, there is also a mathematical term with the abbreviation of "ch", that is "Kramer-Hastings Matrix". This matrix is a coefficient matrix of linear equations with unknown variables, which has been widely used in many fields of mathematics, especially in statistics. For linear equations with n variables, each column of kramer-Heston combination matrix contains n necessary coefficients to solve the unknown variables of the equations.

Let's put aside the meaning of the abbreviation "ch" in mathematics and look at the common usage of this abbreviation overseas. In English, ch is usually the abbreviation of "channel", which means a certain channel or channel. For example, in the field of TV or radio, people often say that "tuning to channel 7" means tuning to channel 7. In addition, in the field of computer network, the abbreviation ch is often used to refer to the "client-server" architecture, such as "P2P over ch", that is, data is transmitted in a peer-to-peer manner through communication between the client and the server.