Difference between statement, expression and block (statement, expression and block)

An expression is a piece of code that results in a quantity. The instruction is a code fragment that changes the state of the environment in which the program is running.

I took this definition from a javascript book ( http://eloquentjavascript.net/ ), I think it works in the context of any language. But still curious: how it is exhaustive.

From the definition follows:

• sum = 2 + 3; - instruction containing an expression
• var sum; - just an instruction without expression
• 2 + 3; - just an expression, but expressions without instructions are meaningless (except when debugging) because with the result you need to do something / store it somewhere.

Block - a set of several instructions.

Expression ( Eng. Expression ) - an instruction that assigns the right side of the expression to the left side (expresses the left side through the right side).

The instruction ( eng. Statement ) is in programming, a programming language command that specifies a certain step in the processing of information on a computer.

1. Any expression is an instruction.
2. Not every instruction is an expression.

Code example:

a = 1; выражение int a = 10; инструкция и выражение (сначала [var a] — инструкция которая не является выражением т.к. присваивания нет, а потом уже [a = 10] — выражение, которое можно также назвать инструкцией). if (a < 2){} else{} и т.д. — инструкция, но не выражение, ибо ничего не выражается, но действия происходят. Точно также и с w = x+y+z : 1. x+y+z // инструкция, но не выражение. 2. w = //если вы введете сюда код что вернула инструкция (x+y+z) — выражение и инструкция присваивания одновременно 

A block (English Block) is 0 or more instructions placed between curly braces and can be placed in the place where the code is allowed. For example:

  class BlockDemo { public static void main(String[] args) { boolean condition = true; if (condition) { // начало блока 1 System.out.println("Condition is true."); } // конец блока 1 else { // начало блока 1 System.out.println("Condition is false."); } // конец блока 2 } } 

References to sources:
https://docs.oracle.com/javase/tutorial/java/nutsandbolts/expressions.html http://javascript.ru/forum/misc/25447-raznica-mezhdu-vyrazheniyami-i-instrukciyami.html