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Mixed square and round brackets marking whether an endpoint is included.
Also known as: Interval notation, Open and closed brackets, Range notation
Interval notation writes two endpoints separated by a comma, with the bracket at each end saying whether that endpoint belongs to the interval: a square bracket includes it and a round bracket excludes it. The two ends are independent, so a half-open interval mixes the two. A European convention uses a reversed square bracket in place of the round one, which is unambiguous once known and baffling on first sight.
Says at each end whether the endpoint belongs to the interval: a square bracket includes it and a round bracket excludes it, and the two ends are decided independently.
Contexts: Mathematics
Has a European variant that reverses a square bracket instead of using a round one, so that an outward-facing square bracket excludes the endpoint. It is unambiguous once known and unreadable before.
Continental Europe · Contexts: Mathematics
Two numbers separated by a comma, with a square-cornered bracket or a curved bracket standing at each end, the two ends often differing from one another.
Both write down a set without listing its members.