「は」vs 「が」 in subordinate clauses

Question

I'm confused about「は」vs「が」 in subordinate clauses. Here are a few examples from (very basic) grammar books:

1. 僕が 電話したとき、ナツミは もういなかった。When I called, Natsumi had already left.

2. 弟が 日本に来たら、私は 日光に連れて行きたい。When my brother comes to Japan, I want to take him to Nikkou.

3. 地震は 私が 結婚した年に起こった。The earthquake happened the year that I got married.

4. 東野さんが 薦めてくれた本は 何でしたか。What was the book that Mr. Higashino recommended?

5. 武が 昨夜見た映画は 楽しかったですか。Did you (Takeshi) enjoy the movie that you saw last night?

6. 私が それを見た場所は そこにあります。The place where I saw it happen is over there.

I am aware that you can't use the same particle in a subordinate clause that you used in the main clause, but how do you know which one should be は, and which one が? Does it simply depend on which part of the sentence you want to emphasize? Does it matter whether the subordinate clause is a noun, adjective or adverb?

If the instances of は and が in the above examples were reversed (each は in place of each が) would this be incorrect, or would it simply change the nuance?

Answer 1

は serves as the topic marker of the main clause. In subordinate clauses, basically you cannot use は. You have to use が to mark a subject in subordinate clauses. (There are exceptions, which I will mention later, but all your examples are simple ones that can be explained without knowing the exceptions.)

It appears to me that you are confused because you don't understand which part of your examples actually belongs to a subordinate clause. So here are the subordinate clauses in your example sentences:

• 1: 僕が電話した is a relative clause that modifies the noun とき. (This construction is usually translated into English as "when ～" without using an English relative clause.)
• 2: 弟が日本に来たら is a subordinate clause which is not a relative clause.
• 3: 私が結婚した is a relative clause that modifies 年.
• 4: 東野さんが薦めてくれた is a relative clause that modifies 本.
• 5: 武が昨夜見た is a relative clause that modifies 映画.
• 6: 私がそれを見た is a relative clause that modifies 場所.

(A relative clause is a type of subordinate clause that works like an adjective. They "adjectivally" modifies the following noun. In your example, all but Sentence 2 are using relative clauses. There is a good answer about relative clauses.)

As you can see, the basic rule is very simple: が is consistently used in subordinate clauses regardless of the type.

If you are still confused, remember that a subordinate clause can appear anywhere in a sentence to modify something. The word marked with は is the topic of the main clause, at least in your examples. No emphasis/contrast is concerned.

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There are a few exceptions you will encounter sooner or later. You can forget these for now if you feel these are too difficult.

• In relative clauses, の can be alternatively used instead of が to mark a subject in many cases. See: How does the の work in 「日本人の知らない日本語」? Among your examples, の can be used instead of が in Sentences 1, 3, 4 and 5. (But not は!)
• は can be used anyway in subordinate clauses if it's used as a contrast marker. See: Is saying 「XはYは…」 acceptable?