Translatable but Debatable
I notice that when you use Microsoft Outlook to schedule a meeting, you invite attendees (הזמנת משתתפים), and they can be required attendees or optional attendees (דרושים or אופציונליים). The idea of a required attendee is ambiguous in a way that the people care about more than the software does. It could mean that the meeting must respect the schedule of the required attendee, or it could mean that the required attendee must respect the scheduling of the meeting. The difference is like the difference between a הזמנה and a זימון in Hebrew.
The word הזמנה is the one that corresponds better to invitation. It’s a notice saying that you will be welcome at the specified place at the specified time, but unlike זימון it implies you are free to never show up. A זימון may be open to negotiation, but it does not want, and it does not expect, to be disregarded.
If it is “a call by authority to appear at a place named or to attend to a duty,” and especially to appear in court as a defendant or witness, then the Merriam-Webster dictionary calls it a summons.
But not every זימון is a summons. It can be less imperially unilateral. If you want to register as a marrow donor, you might phone the lab, agree on a mutually convenient date, and receive a זימון for that date. It’s still a זימון because the relationship is asymmetrical — they’re the important institution, whereas you’re the mere layman — and because once they’ve issued it, you’d better not miss the appointment.
There are dictionaries that use the words appointment and assignation as definitions of זימון, and you would not be surprised to receive a זימון in English that said Appointment at the top. But a זימון is not an appointment, it is a notice that cements an appointment. If a spouse says “What are you reading, dear?” it sounds strange to answer “I’m reading my appointment to register as a marrow donor.”
Rephrasing is not necessarily difficult: Instead of “I’m reading my appointment,” you could say “I’m reading about my appointment,” for example. But does anyone have a good direct translation, without rephrasing — an English word for the kind of זימון that comes from the medical lab, the big insurance company, the casting director? If so, please comment below. Anyone can comment; just please stay on topic. If you have something to say that isn’t about זימון or הזמנה, and especially if you have another word to bring up for discussion, please write me at firstname.lastname@example.org.