Are the following sentences both correct? If so, what's the difference?

The disease varies with severity.

The disease varies in severity.

  • When we say X varies with Y, we mean that whenever Y changes, X also changes. For example, The prognosis for Covid varies with age (because it usually affects older people different to younger people). But X varies in Y means there is some characteristic (Y) that occurs in a range of different forms among instances of X. For example, The disease varies in severity (in part, ...depending on how old you are). Dec 10, 2020 at 18:30

1 Answer 1


Varies in severity means the severity of the disease is not constant. It varies.

Varies with usually means that something varies according to something else. For example,
The severity of the disease varies with the age of the sufferer.

It is strange to say that a disease varies with severity. I would even say that that example doesn't make sense.

  • How about "The symptoms of the disease vary with its severity"?
    – Apollyon
    Dec 10, 2020 at 18:35
  • That makes sense. Dec 10, 2020 at 18:36
  • Clutching at straws, The prognosis for the disease varies with severity of economic hardship (people suffering from severe economic hardship often have a different outcome). Dec 10, 2020 at 18:37

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