Yap.Town

の会員だ

be a member of

→ の
phrase Rare #29,165
be a member of Used after the name of a club, organization, or group. The polite form is の会員です, and の会員である is a more formal written form.
JA: 彼はこのスポーツクラブの会員だ。
EN: He is a member of this sports club.

トムは全米ライフル協会の会員だ。

Tom is a member of the National Rifle Association.

トムは読書会の会員だ。

Tom is a member of the book club.

メアリーは読書会の会員だ。

Mary is a member of the book club.