IPA: /nɒnˈmɛmbəʃɪp/
KK: /nɑnˈmɛmbərʃɪp/
The state of not being a member of a group or organization.
Her nonmembership in the club meant she couldn't participate in the events.
Nonmembership → It is formed from "non-" (meaning not) and "membership" (from Old English "membrescipe", meaning the state of being a member). The word "nonmembership" means the state of not being a member.
Think of 'not' ('non-') being combined with the 'state of being a member' ('membership') to remember that 'nonmembership' refers to not being part of a group.