Learn Hardcore Japanese: sono kotae ha matigatte imasu.

その is a demonstrative adjective meaning “that,” referring to something the listener already knows or that’s been mentioned. Here it points to 答え (“answer”) that’s understood in context.

Why is the particle は used after 答え, and could I use が instead?

は marks 答え as the topic (“as for that answer…”). It sets up what you’re talking about. Using が would mark 答え as the subject and emphasize it as new or specific information. In this case, その答えは間違っています sounds most natural because you’re commenting on a known answer rather than introducing it for the first time.

What is 間違っています, and why not just 間違う?

間違って is the –te form of the intransitive verb 間違う (“to be wrong”), and ～ています expresses a resulting state or continuous condition. So 間違っています means “is (currently) wrong.” If you said 間違う, you’d only state the action “to be wrong” without indicating it’s an ongoing state in the context.

Could I say その答えは間違いです instead, and what’s the nuance?

Yes. その答えは間違いです uses the noun 間違い (“mistake”) with the copula です, so it literally means “that answer is a mistake.” It’s slightly more formal or textbook-like. 間違っています focuses on the action/state (“is wrong right now”), while 間違いです labels it as a mistake.

How do you pronounce 答え, and why is it written with Kanji plus え?

It’s pronounced こたえ (ko-ta-e). The Kanji 答 carries the core meaning “answer,” and the hiragana え is the inflectional ending that turns the verb or action into a noun form. Writing it this way is very common in Japanese for many words that combine Kanji and hiragana.

Why is there no English-style subject like “it” or “this answer” at the start?

Japanese often omits subjects when they’re clear from context. Here, その答え is enough to show what you’re talking about, so there’s no need for an extra pronoun. The language relies on context rather than explicit subjects.

What’s the difference between 間違う (intransitive) and 間違える (transitive)?

間違う is intransitive: “to be wrong” or “to make a mistake” in the sense that something itself is incorrect. 間違える is transitive: “to mistake A for B” or “to get something wrong” in the sense of confusing one thing with another. In our sentence, we describe the answer itself as wrong, so we use 間違う.