A single word for non-unique?

A naming question:

I am aware that this question is about use of English, and at first thought should be asked in the English sub, but people there don't like questions like this, so I am trying my luck here...

I have a bunch of non-unique values:

   const nonUnique = getSomeValues();

now I want to make sure I have only unique ones:

   const unique = keepUnique(nonUnique);

How else can I name nonUnique to

• preserve the meaning: a bunch of non-unique values
• avoid using negation
• have just a nice single word that is opposite to unique in the described sense

?