Breakdown of ציר המשקפיים הוא חלק ממסגרת המשקפיים.
Questions & Answers about ציר המשקפיים הוא חלק ממסגרת המשקפיים.
Here ציר means hinge.
More generally, ציר can also mean things like axis, pivot, or axle, depending on context. But with glasses, the natural meaning is hinge — the small joint that lets the arm of the glasses fold.
Yes — משקפיים is a plural/dual-form noun.
The ending ־יים often marks the dual in Hebrew, especially for things that come in pairs. A native English speaker can think of it a bit like words such as glasses, pants, or scissors, which are normally talked about in the plural in English too.
So משקפיים is the normal word for glasses or eyeglasses, and it usually appears in this form rather than as a regular singular noun.