What's the difference between metalanguage symbols and object language symbols?

Human language is a complex symbol system, which consists of three parts or three factors: basic symbols, morphological rules and semantic rules. Take Chinese as an example, every word is a basic symbol, and basic symbols are the basic materials of language; Chinese grammar is a morphological rule, which stipulates which combinations of words are grammatical; A word can refer to a specific object and a sentence can express a specific meaning, which is stipulated by semantic rules, which are the interpretation of words, phrases and grammatical sentences.

By adopting different standards, languages can be classified differently. Such as spoken and written language, natural language and artificial language, metalanguage and object language. The latter two classifications are necessary for learning logic.

Natural language is a language gradually formed by people in long-term social activities. The languages used by all ethnic groups, such as Chinese, English and German, are all natural languages. Compared with artificial language, natural language is more basic, because the creation of artificial language always depends on natural language. Natural language has two characteristics: first, natural language is established by people in long-term social practice, and the meanings expressed by words or sentences are often diverse and vague. Second, natural language is usually vague, and the same word or sentence can express different meanings in different contexts. These characteristics of natural language may lead to misunderstandings in daily communication, and may also bring some inconvenience to research. For example, in philosophical research, scholars often argue about different understandings of some documents. Traditional logic regards natural language as a tool language, and its research object is mainly expressed by natural language. The fuzziness of natural language itself makes traditional logic have some defects.

Partly due to the fuzziness and ambiguity of natural language, artificial language is produced in logical research. Artificial language is a language specially created by people for some scientific research or other specific purposes. Mathematical language is a typical artificial language, as is the semaphore used by traffic police and the assembly language used by computer programming. The artificial language used in modern logic is called symbolic language, which is why modern logic is also called symbolic logic. The biggest feature of symbolic language different from natural language is that the symbols it uses are strictly defined and have a single meaning, and everyone's understanding of the same symbol is completely consistent. Modern logic uses such symbolic languages and mathematical methods to construct formal systems, so it has the charm of accuracy.

The difference between metalanguage and object language is based on the assumption that language or symbology is hierarchical. When we study a formal system or a language, the symbols and languages as the research objects are object languages, and the tool languages or symbols used in the research are metalanguages. For example, we use Chinese to learn English grammar. English is the target language and Chinese is the metalanguage. We can also distinguish between object language and metalanguage in a language. If we want to study metalanguage, we need to use metalanguage. In modern logic, object language is symbolic language, and metalanguage may be natural language or symbolic language. The difference between metalanguage and target language is very important in subsequent learning.