Bracket

They are used in mathematics and in literature (written language). They are sometimes used to set apart or interject other parts of the text. They are noted as left/right: the left bracket is "[" and the right bracket is "]".

In the American English, "bracket" usually refers specifically to the "square" or "box" type. In British English, "bracket" normally refers to the "round" type, which is called a "parenthesis" mark in American usage.

Parentheses are the curved brackets "(  )". They are also called round brackets, curved brackets, oval brackets, or, colloquially, parens.

Parentheses have several different meanings, such as:

• noting optional text:  "(this is optional)";
• showing other word endings:  "vote(s)" or "quick(ly)"
• adjusting the meaning:  "There are some (many) pages".
• adding humor:  "They sell pre-owned (read: "used") cars".
• indicating a negative number:  $90 - $100 = ($10)
• grouping terms in a calculation:  6 x (2 + 3) = 30.
• showing emphasis for attention:  "(((wow)))".

There are also other uses for parentheses.

Parentheses enclose text which could be left out, without destroying or altering the meaning of a sentence. In most writing, overuse of parentheses is usually a sign of a badly structured text. A milder effect may be obtained by using a pair of commas around the text, although if the sentence contains commas for other uses, then visual confusion may result.

Parentheses may be used in formal writing to add more information, such as in:

"Sen. John McCain (R., Arizona) spoke at length"

They can also note "either singular or plural" for nouns, such as in the word "claim(s)".

In mathematics, various brackets are used for various purposes. These include, in particular:

• The use of parenthesis in ordered pairs and tuples (as in ${\displaystyle (3,5,12)}$)
• The use of square brackets in intervals (as in ${\displaystyle (3,4]}$)
• The use of braces in set-builder notation (as in ${\displaystyle \{\pi ,e,i\}}$)
• The use of angle brackets in inner products (as in ${\displaystyle \langle a,b\rangle }$)

• Emoticon
• Order of operations