How to change language by different system?

Hi Basis Guru,

There are multi systems in SAP.

I want to change language to one of the systems by that system's options:

After I log off and log on again, the language keeps the same. not changed.

The only way I can do is the language change at SAP application level:

But it applies to all SAP systems.

I gather it is some settings related to Basis.

Please kindly help me.

Sally