I'd like to know the definitions of both mathematical terms "consistency" and "completeness". Would I ask

  • "What are consistency and completeness?" (i.e., the two nouns are singular, but together they're a collection of things) or
  • "What is consistency and completeness?" (i.e., we can distribute the "What is" to read "What is consistency and what is completeness?")


marked as duplicate by user140086, Nathaniel, Mitch, choster, Benjamin Harman Jan 16 '16 at 19:26

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What are X and Y? asks for separate definitions of each term. It's like What is X and what is Y?.

What is X and Y? treats them as a single collective concept, and asks for a definition of that one thing.

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