Question: I'm trying to grasp the difference between *Kugel* and *Ball*.

So I took such spiky toy ball kugel thing:

[![spiky toy ball kugel thing](https://i.stack.imgur.com/4CAzl.jpg)](https://i.stack.imgur.com/4CAzl.jpg)

and went to ask a German person what that was. "It's a *Ball*", he said. "Because it's shaped like a *Kugel*, but a *Ball* is serving a greater purpose and is not about the geometric shape." (He really said that!)

So I asked him if a marble ball is more of a *Ball* than a *Kugel*.
This is what a marble balls looks like:

[![marble ball](https://i.stack.imgur.com/rmZyt.jpg)](https://i.stack.imgur.com/rmZyt.jpg)

He said, that's definitely more of a *Kugel* over a *Ball*. I asked him if marble balls had no greater purpose and he said he didn't know. :(

Well, now I'm super confused.

Somewhere I have read that every *Ball* is also a *Kugel*. And a *Ball* is made of flexible material. But that's not true in all cases, is it? I couldn't really find a satisfying answer to that on the Internet.

Answer: 
The confusion may be sorted a bit if we have a look at the etymology of both words.

> 
> * [Ball](http://www.dwds.de/?qu=Ball)  
> 
>  goes back to the indo-european root `*bhel-` in the meaning of *inflated*, *swollen*. It is the same root for the English *ball*, and we also find it in the greek φαλλός (*phallus*).
> * [Kugel](http://www.dwds.de/?qu=Kugel)
>  goes back to the indo-european `*gugā` for a *bent* or *curved* body.
> 
> 
> 

So whenever we use *Kugel* there is a reference to the **shape** of the body (as also used in the mathematical term) whereas when using *Ball* we refer to the **consistence**, and springiness of a mostly spherical body.
I think some of the confusion might derive from the different use of the word of "ball/Ball" and "sphere/Kugel" in English and German:

Ball: in German, "Ball" is related to the construction of the item, i.e. it has a shell and something in the centre (typically air), and is designed to bounce back. Hence a football is a "Ball", but a snooker ball is a "Kugel". 
There is a slight connotation of that a "Ball" is designed to play games, but I think this rather derives from the fact that they usually are used this way, rather than this being part of the inherent meaning of the word.

Kugel: is a "sphere" in the mathematical sense. In the everyday sense however, it is a ball (English) which is solid, i.e. fully filled with material and does not have a shell. If I did not know the word for Jan's mentioned "Murmeln", I would definitely call them Glaskugeln (and not Glassbälle).