を(o) — Direct Object & Traversal

• 本を読みます。

  Hon o yomimasu.

  I read a book.

  本 (book) を (object) 読みます (read)

• 公園を散歩します。

  Kouen o sanpo shimasu.

  I take a walk through the park.

  公園 (park) を (space traversed) 散歩します (walk)

• 電車を降ります。

  Densha o orimasu.

  I get off the train.

  電車 (train) を (point of departure) 降ります (get off)

• ・Pronunciation & romaji: The kana を is written 'wo' in kana charts but pronounced 'o', and modified Hepburn romanizes it as 'o'. It is used ONLY as a grammatical particle.
• ・Traversal: Motion verbs that pass through a space (歩く walk, 走る run, 飛ぶ fly, 通る pass, 曲がる turn) use を to show where the movement takes place.
• ・Departure: Verbs of leaving/exiting (出る leave, 降りる get off, 卒業する graduate) use を for the place left behind.

Commonly confused with

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

• は (wa) — Topic & Contrast Particle
• が (ga) — Subject Marker & Exhaustive Listing
• 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
• も (mo) — Also, Too, Both/And, Emphasized Quantity