が(ga) — Subject Marker & Exhaustive Listing

• 雨が降っています。

  Ame ga futte imasu.

  It is raining.

  雨 (rain) が (subject) 降って (falling) います (continuous)

• 私がやります。

  Watashi ga yarimasu.

  I will do it (not anyone else).

  が singles out 'I' as specifically the one who will do it (exhaustive/identifying)

• 犬が好きです。

  Inu ga suki desu.

  I like dogs.

  好き (like), 嫌い (dislike), 欲しい (want) take が for their target

• ・Question Words: Question words as subjects (誰, 何, どこ) MUST take が, never は (e.g. 誰が来ましたか？).
• ・Object Marking: Words of preference (好き/嫌い), desire (欲しい/たい), and ability (できる/分かる) take が, not を, for their target.
• ・Subordinate Clauses: The subject inside a modifying clause ('the book [that I bought]') takes が: 私が買った本, never は.
• ・Conjunction: が at the end of a clause means 'but' (行きますが… = I'll go, but…).

Commonly confused with

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

• は (wa) — Topic & Contrast Particle
• 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
• も (mo) — Also, Too, Both/And, Emphasized Quantity