[wilg]

As an American, I'm constantly confused by this when watching UK television.

I would call the [ a "bracket", and only if I had to clarify would I say "square bracket" to distinguish it from a curly brace { (which is sometimes called a curly bracket) and I don't think most Americans would even consider a ( a type of bracket at all.

If I had to come up with a rationale, I would say that physical brackets are almost always more square than round, and a bracket graphic in the sense of a sports bracket is also usually square, so brackets are square!

[marssaxman]

I asked "which dialect of English calls parentheses 'brackets'", but apparently I got it backwards, and it's only US English which makes the distinction!

[devidw]

Thanks a lot, clarifying this from the US perspective. Will consider coming up with a less misleading naming.

[gumby]

I actually prefer the US usage, as "parenthesis" is such a lovely metonym that describes the thing it encloses.

People are used to indicating so anyway in speech (referring to a parenthetical remark). And while in writing parentheses can acceptably be set off in a variety of ways, I have a fondness for the good old parenthetical brackets.