The right hand side of the above equation has two terms in the outer square bracket.
In particular, the last four terms in the square bracket describe such effects.
The field itself should end in a period unless a hyphen, question mark, or square bracket is already present.
The square bracket operator can be used to build arrays.
British Dictionary definitions for square bracket
square bracket
noun
1.
either of a pair of characters [ ], used to enclose a section of writing or printing to separate it from the main text
2.
Also called bracket. either of these characters used as a sign of aggregation in mathematical or logical expressions indicating that the expression contained in the brackets is to be evaluated first and treated as a unit in the evaluation of the whole