The question of whether or not zero is a number is not a question about what zero is and what it means; it is a matter of how we choose to define the term “number”, whether we choose to apply the label “number" to the conceptual entity we call zero.
So the definition of the word “number” is such zero is a number. This makes perfect sense, of course; it would be bizarre if what we call negative numbers were regarded as being numbers, but zero was not.
In conclusion, then; zero is a number, by definition.
