玉と球

Question about Japanese
What is the difference between 玉 and 球?

球 means a ball, which is used for throwing or hitting. So almost all kind sof ball sports are named by using "球".
Such as:
野球 baseball
蹴球 soccer
籠球 basketball
水球 water polo
排球 volleyball
撞球 billiards
(The pronunciation of "球" is "きゅう(kyuu)" for above all cases).

Originally, in ancient Japan, 玉 meant jewel (ex. jasper, jade stone ).
玉 is pronounced as "ぎょく(gyoku)" for this meaning.

In the old days in Japan, jewels were cut, ground and polished as round shape.
So the word 玉 got a new meaning of "round shaped thing". The pronunciation is "たま(tama)" for this meaning.

Compared to 球, there are some differences.

球 is more rounded, more ball like shape.
玉's shapes are more freestyle. Include not ball like shape, such as: a teardrop, a curved teardrop ( you can see examples of curved teardrop shaped 玉's at the URL https://www.google.co.jp/search?q=%E7%8E%89&espv=2&biw=1280&bih=939&source=lnms&tbm=isch&sa=X&ved=0ahUKEwizlL-7mL7OAhUDE5QKHbzGCR4Q_AUIBigB#tbm=isch&q=%E5%8B%BE%E7%8E%89 ), or oval shape, and so on.