Inorganic chemistry

What is the exact definition of Inner transition element?I have read three definitions as follows-
(1) Inner transition elements are the elements in which either in their ground state or in their most stable oxidation state partially filled f orbital is present.According to this definition all f-block elements except Lu and Lr are inner transition elements
(2)Inner transition elements are f block elements.According to this all f-block elements are Inner tranistion elements.
(3) f-block elements which have incompletely filled outermost shells,penaltimate shell and antipenaltimate shell are called inner transition element.As Lu and Lr has completely filled antipenaltyamte shell so they should not include in this category.
Please tell me which is correct and It will be thankul if anyone can provide some reference also.

Hi Satwant,
You have stumbled upon one of the gray areas of chemistry. Definitions sometimes vary region to region, meaning that there isn’t a universally-accepted definition. You’re better off asking your teacher for the definition you’re expected to follow.