unite
verb
•come or bring together for a common purpose or action: [no object]: he called on the party to unite [with object]: they are united by their love of cars
•come or bring together to form a whole: [no object]: the two Germanys officially united [with object]: his work unites theory and practice
•[with object] archaic join in marriage: Lady Midlothian united herself to a man of bad character
Join
verb
[with object]
•link; connect: the tap was joined to a pipe join the paragraphs together
•become linked or connected to: where the River Drave joins the Danube
•[no object, with adverbial] unite to form one entity or group: they joined up with local environmentalists countries join together to abolish restrictions on trade
•become a member or employee of: she joined the department last year
•take part in: I joined the demonstration [no object]: I joined in and sang along
•[no object] (join up) become a member of the armed forces: her brothers joined up in 1914
•come into the company of: after the show we were joined by Jessica’s sister
•support (someone) in an activity: I am sure you will join me in wishing him every success
