What exactly are C++ definitions, declarations and assignments?

Question

I tend to use the words define, declare and assign interchangeably but this seems to cause offense to some people. Is this justified? Should I only use the word declare for

Answer 1

General Role: Definition = declaration + reserved space.

Definition, declaration, and assignment have two cases:

1. for Variables.
2. for Functions.

---

For Variables:

-- Definition:
To tell the compiler to reserve memory for the variable.

int x;

-- Declaration:
To tell the compiler that the variable defined in somewhere else.

extern int x;

-- Assignment:
To tell the compiler to put the value in the variable.

x = 0;

---

For Functions:

-- Definition:

int functionDef(int x){
  int x;  
  ...  
  ...  
  ...  
  return x;  
}

-- Declaration: It is just the prototype of the function.

int functionDef(int x);