4 ms·

Probably for the same reason that some people refer to regular calculus as "the calculus".

• commandlinefan 7y ago
  You'll always sound smart if you remember that "maths" is plural and one of them is "the calculus".
  • leadingthenet 7y ago
    Maths is the common spelling and pronunciation in standard British English, though.
  • lonelappde 7y ago
    There are many calculi
  • deleted 7y ago
    [deleted]