definiens: or CO - COMMERCIALIZATION " shall mean ( a ) co - promotion meaning that each co - promoting PARTY promotes sales of the same product under the same trademark and revenues are shared based on the relative contributions of both PARTIES, ( b ) if the co - promotion activities described in ( a ) are commercially impractical or illegal in a particular country, or if the PARTIES so agree, then CO­COMMERCIALIZATION shall mean co - marketing, meaning that each co - marketing PARTY performs marketing of the same product under different trademarks for its own account, ( c ) if the PARTIES so agree, MERCK KGAA marketing a PRODUCT alone on a country - by - country basis, or ( d ) any other joint promotion, or marketing arrangement with respect to a PRODUCT, and ( e ) if MERCK KGAA elects to CO - COMMERCIALIZE pursuant to Section 5.3.1, co - development whereby the PARTIES share in development costs, whether by funding or by sharing in development activities