when i go to

https://en.cppreference.com/cpp/language/constexpr

it says

constexpr variable

A variable or variable template(since C++14) can be declared constexpr if all following conditions are satisfied:

• The declaration is a definition.

when i click on definition it takes me to :

https://en.cppreference.com/cpp/language/definition

is the cppreference trying to explain the difference between declaring and defining ?

what i understand is it tries to tell me that if i used

constexpr int start

i have to define it as well i should not just declare it so i have to do this :

constexpr int start = 9;

is my understanding right ?