duplicate

Everyday

1. (noun) An exact copy of something, such as a key or a document. tree →
2. (verb) To make an exact copy of something. tree →
3. (verb) To do something again that has already been done, wasting effort. tree →
4. (adjective) Exactly the same as another; made as a copy. tree →

In the lessons

Used for keys, cards, files, photos and paperwork: «a duplicate key», «in duplicate» (in two copies). In computing and data work, «duplicates» are repeated items that should be removed. In maths and science, experiments are duplicated (done twice) to check the results. In card collecting, «duplicates» or «swaps» are spare copies.

Examples

• Dad had a duplicate key made for the shed. tree →
• I have three duplicates of this football card, so I'll swap them. tree →
• The form must be filled in in duplicate. tree →
• Delete the duplicate photos to save space. tree →
• Scientists duplicated the experiment to check the result. tree →
• Let's not duplicate work: you do the poster and I'll do the speech. tree →
• The printer duplicated the page by mistake. tree →
• Remove the duplicate numbers from the list 4, 7, 4, 9 and you get 4, 7, 9. tree →

Note

The noun and adjective are pronounced DYOO-pli-kut; the verb is DYOO-pli-kayt. «In duplicate» = two copies. Related: «duplication». In maths and data, «duplicates» are repeated values; counting a list «without duplicates» means counting each value once.