1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why topological invariants instead of topological invariances?

  1. Nov 20, 2013 #1
    Isnt it invariant an adjective?
  2. jcsd
  3. Nov 20, 2013 #2


    User Avatar

    Staff: Mentor

    Because that's the way English is.

    "Invariant" is indeed an adjective, but it is also a noun referring to something that has the property of being invariant. In the (tautological) sentence "I know that this quantity is an invariant because it is invariant", the word "invariant" is used twice, once a noun and once as adjective.

    And "invariance" is also noun, but it refers to the property that is described by the adjective, not to an object that has that property: "I know that this quantity is an invariant because is invariant, which is to say that it has the property of invariance".

    English is weird. I love it for its quirkiness and expressive power, but it's still weird.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook