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What is the proper name or terminology of notation for using a comma to separate and group thousandths of a number?

As in, formatting large numbers for readability:

comma delimited    real number
          1,000           1000
         10,000          10000
        100,000         100000
      1,000,000        1000000

How would you refer to this grouping of every third digit?

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up vote 1 down vote accepted

Thousand separation or digit grouping.

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Perl users use the term "commify", probably a reference to "sub commify" in the Perl FAQ "How can I output my numbers with commas added?".

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