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One-to-one function, also called an injective function •
One-to-one correspondence, also called a bijective function •
One-to-one (communication), the act of an individual communicating with another •
One-to-one (data model), a relationship in a data model •
One to one computing (education), an initiative for a computer for every student •
One-to-one marketing or personalized marketing, an attempt to make a unique product offering for each customer ==Music==