Trademark right can be transferred or assigned to others for valuable consideration.
Transfer of trademark right can be done by way of sale , exchange etc .
Assignment Trademark right can be done in the form licence or permission for using the right for a particular period, products etc.
The Trademark right devolve to others in such instance as the death of the registered owner, amalgamation of firms & companies etc. This is technically know as transmission of trademark right.
Whether it be a transfer , assignment or transmission of a trademark right, it has to be properly documented considering all the niceties of existing laws and registered with registrar of trademarks.
Trademark attorneys at tmkerala can help you on transfer, assignment or transmission of trademark rights.