c++ - Declaring, defining, assigning, initialising variables -

this in reference c++. question have goes 6 months, when used think declaration was:

int a; 

and definition was:

a = 5; 

also, that:

int = 5; 

was both declaration , definition.

i've come understand that:

int a; 

is definition, not declaration. (i don't know why).

also, there terms such assigning, , initialising add further jargon issue.

so here current understanding (and please correct anything):

int a;    // declaration , definition  int = 5 // declaration, definition, assignation , initialisation.  = 5;    // initialising (if first time),           // assigning (if subsequent times),           // defining (not sure one). 

i have read quite bit on topic still confused. can explain each is? know in such cases there philosophical disputes, 0 number, or number. haha, can try? thanks.

a declaration may introduce 1 or more names translation unit or redeclare names introduced previous declarations.

a definition declaration in specific circumstance. (ie, declaration initializer). because have meet 1 definition rule. definitions declarations, not vice-versa.

initialization gives initial value variable in definition. initialization happens in other situation (eg. function argument passing)

assignment used assign new value existing object.

in specific case

int a;    // definition, default-initialization if it's local, zero-initialization otherwise int = 5; // definition, copy-initiaization = 5;   // assignment 

also, following declaration not definition

extern int i;  // declaration not definition