The reason why some adjectives and names are bracketed and some are not: This is a writing standard, just like writing from left to right in ancient times. Names in brackets generally indicate the author of the article.
used to mark international phonetic symbols: most international phonetic symbols are printed in lowercase in Latin letters. Some of them are slightly modified or have additional symbols, and square brackets are added to indicate that they are phonetic symbols, not letters. For example, there are three factors [i], [u] and [y] that can act as a mediator in Beijing dialect.
mathematical usage of brackets:
brackets are symbols used to specify the operation order.
The earliest parenthesis is the parenthesis "()", which appeared in 1544. It was not until the 17th century that the brackets "[]" appeared in the works of Varis (1616-173) in England, and the enclosed line was first adopted by Veda (154-163) in 1591.
The brace "{}" was first introduced by Wei Da in about 1593, which is mainly used to represent a set of numbers. By 1629, the Dutch Kirad had adopted all the brackets, and it began to be used in the world after the 18th century.
With the deepening of mathematics learning, all brackets can be replaced by "()", which looks convenient and can avoid the situation of too few bracket styles.