や(ya) — Non-Exhaustive Listing Particle

• カバンにペンや本があります。

  Kaban ni pen ya hon ga arimasu.

  In my bag there are pens, books, and things like that.

  Implies other unmentioned items (phone, keys, etc.) may also be in the bag.

• 机の上に本やノートなどがあります。

  Tsukue no ue ni hon ya nooto nado ga arimasu.

  On the desk there are books, notebooks, and so on.

  や links NOUNS (本 / ノート) and is commonly closed off with など (etc.).

• 朝ごはんにパンやたまごを食べました。

  Asagohan ni pan ya tamago o tabemashita.

  For breakfast I ate bread, eggs, and things like that.

  や links パン and たまご, implying the breakfast included other items too.

• ・Nuance (や vs と): 「お茶と水」 claims exactly tea and water, nothing else. 「お茶や水」 suggests tea, water, and possibly coffee or juice too.
• ・Safety Rule: や links ONLY nouns. You cannot use や to join two verbs or two adjectives — use the て-form or 〜たり for those.

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones や is tested against.

• は (wa) — Topic & Contrast Particle
• が (ga) — Subject Marker & Exhaustive Listing
• を (o) — Direct Object & Traversal
• に (ni) — Target, Time, and Existence Location
• で (de) — Context of Action (Location, Means, Condition)
• と (to) — And (Exhaustive), With, and Quotation
• か (ka) — Question, Or, and Uncertain Identity
• の (no) — Possession, Modification, & Nominalization