This is probably debatable. Expressions are somewhat implicit because you need to be told what to do with them. Functions on the other hand are very explicit; it tells you what it needs and it will give you something back.
Remember that math is a language so it has rules (a lot of them). "5" is an expression. So, what's the answer?
- part of the Fibonacci sequence?
- the number before 6?
- half of 10?
So giving an expression without context can be meaningless.
You've seen this a thousand times:
To be properly define a function, it should always be defined with the function name and its parameters:
Now, if we define something like:
#f(x)=alpha x^2+ beta x+ gamma#
We know, that the only variable (the thing that we can change) is
Yes, it's more work using function notation, but if everyone is clear about what's going on you can use the "=" sign.
I hope this is clear enough.