Consider the following dataset 1, 1, 1, 2, 3

  • Would you have one duplicate because one value has duplicates?
  • two duplicates because there are 2 duplicated values?
  • or three duplicates because the same value occurs 3 times?

If you then remove the duplicate values would you have removed 1 duplicate or 2 duplicates?


I would say there are two duplicates in the set, but I would also say that I am using the word duplicates here to mean duplicate values.

The word duplicate can take on several meanings; one that fits well in this discussion is:

duplicate (n.) One of two or more things corresponding in every respect to each other.

One dictionary adds a pertinent usage note:

duplicate (adj.) being the same as another; identical. This may exclude the first identical item in a series, but usage is inconsistent.

In other words, the first 1 in your dataset would be not be counted as a duplicate, but the next two would be – yet the dictionary acknowledges that this is not a hard-and-fast, immutable rule with no wiggle room for alternate interpretations.

That said, I think it's safe to say that, if you wanted to "remove all the duplicates," you'd remove two members of the set, leaving you with the set {1, 2, 3}.

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Duplicate is synonymous with copy.

If X is duplicated, it means an existing X is used to make a new Y.

Unless this happened with the '1' values in your list, technically they aren't duplicates. You simply have 3 instances of '1'.

The maximum number of duplicates you can have of '1' is 2, because you would have had to use one to "create" the others.

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  • No, "duplicate" doesn't mean created from a previous instance. If I print a file out twice, I have duplicate hardcopies, neither of them created from the other. – Acccumulation Apr 12 '19 at 16:20
  • You created the duplicate hardcopies from an original file which is not a copy. – LawrenceC Apr 12 '19 at 16:48

"Duplicate" implies exactly two copies - one original and one copy.

To convey the meaning of 3 copies, you should use "triplicate".

For more than 3 copies, you should use "copies".

Duplicate is related to double.

Triplicate is related to triple.

Since you do not use double or triple for anything bigger than 3, you do not use duplicate or triplicate for anything bigger than 3, with their respective meanings.

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