ad ‧ join /əˈdʒɔɪn/ BrE AmE verb [transitive]
[ Date: 1300-1400 ; Language: Old French ; Origin: adjoindre , from Latin adjungere , from ad- 'to' + jungere 'to join' ]
a room, building, or piece of land that adjoins something is next to it and connected to it:
A vacant plot of land adjoins his house.
—adjoining adjective [usually before noun] :
adjoining rooms