Linking iBooks to a dictionary

Prior to the installation of iPad's new OS, iBook was linked to a dictionary. Thus, you could select a word and by choosing the define option, you could get a definition.

The new OS does not seem to have this option. The define option is there Utah it is not linked to a dictionary. You have to exit from iBook and go to the dictionary app and then return.

Please let me know if there is a way I can link iBook to a dictionary again.

Many Thanks,
Virstine