When discussing a theoretical distribution having a single parameter described as a degree of freedom (like the $t$ distribution), do we refer to this parameter as degrees of freedom (plural) or degree of freedom (singular). We frequently see expressions such as A t test with 10 degrees of freedom. Could (should) we say A t test with degree of freedom of 10?
I feel that this parameter is a single concept, so discussing it should go with singular? As another example, consider The exact degree of freedom depends on ... Should I write here degree of freedom in its singular form? A reviewer commented that an "s" should be added.
Thanks for this linguistic aid.