head-to-head vs one-to-one

head-to-head

adj

  • Direct, one-to-one. 

adv

  • Directly, one-to-one. 

  • Facing one another. 

one-to-one

adj

  • Involving direct communication between two people. 

  • Matching each member of one set with exactly one member of another set. 

  • Injective, being an injection: having the property that no two elements of the domain are mapped to the same image. 

noun

  • A personal relationship between two people. 

How often have the words head-to-head and one-to-one occurred in a corpus of books? (source: Google Ngram Viewer )