adverb
Etymology: Middle English, from joint + -ly
1. : in a joint manner: as
a. : together , unitedly
activities carried on jointly with other societies — Mech. Engineering
written jointly with other scientists — Current Biography
owned jointly by several companies
specifically : so as to be or become liable to a joint obligation
b. : in joint tenancy or in tenancy by the entirety, or with the right of survivorship
2. : in proportion to the product