What difference, if any, is there between "logo" and "emblem"?
In particular, should "logo" be used for the Tokyo 2020 design that's attracted accusations of plagiarism, or is "emblem" ok as well?
Perhaps it's not an emblem until the games officially open...
The difference is that "logo" has more of a commercial connotation whereas "emblem" has a more traditional, historical meaning. Perhaps it's a "logo" while the national Olympic committee is still working on organizing the event. Once the games are underway, it becomes a worldwide event and stops being identified just with the committee, and thus the logo 'graduates' to being an emblem.
A logo is an art design with inscription of the name and sometimes an animated object that identifies a group like an organization, a nation's coat of arms, or a formation like the military. An emblem is a physical ornamental craft mostly worn by individual members of the organization as an identity. Like the flag of a nation worn on the lapels of jackets, or university alumni.