Synonyms: sign up
Definition: join a club, an activity, etc. with the intention to join or participate, "Sign up for yoga classes"
Definition: become part of; become a member of a group or organization
Usage: He joined the Communist Party as a young man
Definition: engage by written agreement
Usage: They signed two new pitchers for the next season
Definition: engage or hire for work
Usage: They hired two new secretaries in the department; How many people has she employed?