Question: I was trying to understand the [Wikipedia article on homoiconity](http://en.wikipedia.org/wiki/Homoiconicity), but it's too verbose and does not explain the main theory behind the word concisely. I should add that I'm not a native English speaker so I prefer simple English over academic white paper quotes.

So, what exactly does it mean if a language is homoiconic? What makes C#, Java or JavaScript non-homoiconic?

Answer: 
It means "code as data" which is a general characteristic of Lisp family.

```
(add 2 3)

```

Just like above string, which is both a list and also a function call. The "Homo" prefix stands for this characteristic.
Scheme is homo-iconic because its programs have an interpretation as data structures.

```
'(define (foo x) (* x x))

```

is a list, the first element of which is `define`, the second `(foo x)` (a list), and so on. The quote mark `'` means: don't interpret this, leave it as a list. If we remove the `'` we get

```
(define (foo x) (* x x))

```

which is a Scheme function definition. Because Scheme program definitions are nested list expressions (and thereby a sort of "syntax tree literals"), and Scheme is a dynamic language, you can play tricks with this to build very powerful macro/code generating systems.

Now Java isn't homo-iconic simply because it doesn't provide these kind of "program literals" that evaluate to parse tree fragments. Of course, you can define a string

```
String helloWorld =
   "class Hello { public static void main(System.out.println(\"Hello, world!\"); }";

```

which you could parse and feed to a compiler, but that's awkward, because it's a string rather than a structured term.