The symbols on the circuit board in the actual application are not very strict standards (I am talking about the actual application), some use English prefix, some use Khan pinyin, but also use some numbers, symbols, etc., there are also mixed. There are some that we are used to and will not misunderstand, such as: GND (ground, generally refers to the signal ground), COM (common end), VCC, VDD, VSS and so on.
Some are personalized, such as J, some people represent a short wire, some people represent a relay.
CA and RA generally represent a capacitor and resistance array, or only represent a capacitor and resistance. Some symbols are not the same because of different countries and regions, such as printed board sockets in Japan with CN, some with CZ. There are also the same symbols, indicating different contents, such as NC, which represents the normally closed contact of the relay, and the empty foot when used in the integrated circuit.