Learn Hardcore Japanese: watasi ha otouto ni eigo wo osiete miru. - I will try to teach English to my younger brother.

〜てみる is an auxiliary expression that attaches to the て-form of a verb to mean “to try doing something to see what happens.” So while 教える simply means “to teach,” 教えてみる means “I’ll try teaching.” It adds a nuance of experimentation or testing out the action.

Why is みる written in hiragana and not in Kanji as 見る in this structure?

When みる is used as the auxiliary “to try” after a verb’s て-form, it’s conventionally written in hiragana. Writing it as 見る might confuse learners into thinking of the literal “see/watch” verb rather than the auxiliary meaning “give it a try.”

Why do we use 弟に instead of 弟を when saying “teach my younger brother English”?

In Japanese, the person who receives the action is marked with に (the indirect object marker). Since your brother is the recipient of the teaching, you say 弟に. The thing being taught (English) is the direct object, so it takes を.

Why is 英語 marked with を in 英語を教えてみる?

を marks the direct object of a transitive verb. Here, 英語 is what you’re teaching, so it’s the direct object and takes を.

What role does 私 and the particle は play in 私は弟に…? Can we omit them?

私 is the topic, and は marks it as such (“As for me…”). In Japanese, if it’s clear from context that you’re the subject or topic, you can omit 私は and just say 弟に英語を教えてみる. Including 私は simply emphasizes “I, personally, will try teaching.”

What kind of verb is 教える, and how do you form its て-form to attach みる?

教える is an eru-verb (also called a ru-verb). To get its て-form, you drop –る and add –て:
教える → 教え + て ⇒ 教えて.

How do you conjugate 〜てみる into the past tense or polite form?

Since みる here is itself a ru-verb, you conjugate it like any ru-verb:

Polite: 教えてみます
Negative (plain): 教えてみない
Past (plain): 教えてみた
Polite negative: 教えてみません

What’s the difference between the plain 教えてみる and the polite 教えてみます?

The only difference is formality. 教えてみる is casual/plain speech, suitable among friends or in writing. 教えてみます is polite and would be used in more formal situations or when speaking to superiors.

How does 〜てみる differ from the volitional form 〜てみよう or from intention expressed with 〜ようとする?

〜てみる: “I’ll try doing X.” States an action the speaker plans to attempt.
〜てみよう: Volitional form (“Let me/we try doing X” or “I shall try doing X”). Often sounds more like a decision in the moment.
〜ようとする: Emphasizes the act of trying/intending to do X, sometimes with the nuance of “on the verge of doing X.”

Example:
教えてみる (“I’ll try teaching.”)
教えてみよう (“OK, let’s try teaching.”)
教えようとする (“I’m about to try teaching.” or “I’m attempting to teach.”)

Why use 教えてみる instead of 教えてみたい, which also contains みる?

教えてみたい uses たい to express “want to try teaching.” It means “I want to give teaching a try.” In contrast, 教えてみる simply says “I will try teaching” (no explicit “want”). So use ～てみる when you state your intention to try, and ～てみたい when you express desire to try.

Is there any difference between starting the sentence with 私は versus 私が in this example?

Yes. 私は marks “I” as the topic, focusing on what you do. 私が would mark “I” as the subject, often implying contrast or emphasizing that it’s you (not someone else) who tries the action. In everyday speech, 私は is more neutral. Using 私が can make it sound like you’re emphasizing “I, specifically, will try teaching.”