I buy license in themeforest.net but in another domain i cant use theme for wordpress
Each purchase/license is for one website only. If you want to use it on multiple websites then you need to buy new licenses each time.
but i buy theme Newspapper i can use for another domain
Only 1 domain per license.
Every domain/website/project that you want to use it on requires you to buy the theme again
Envato do not offer multi-site licenses