Learn Hardcore Korean: jihacheoreseo chaegeul ilgeoyo.

에서 after 지하철 indicates the location where an action happens (“at/on the subway”). In contrast, 에 marks a static location or destination (“to the subway” or simply “at the subway” without emphasizing action).

Why do we use 을 in 책을?

The particle 을 marks 책 (book) as the direct object of the verb 읽다 (to read). It tells us that the book is what’s being read.

Why is there no subject like 저 or 나는 in the sentence?

Korean often omits the subject when it’s clear from context. Here, “I” (저/나) is understood and doesn’t need to be stated explicitly.

Why does the verb 읽어요 come at the end?

Korean follows a Subject-Object-Verb (SOV) order. You first mention place (지하철에서), then object (책을), and finally the verb (읽어요).

What tense and speech level is 읽어요?

읽어요 is present tense in the polite informal style (요-form). It combines the verb stem 읽- with the ending -어요.

How do you change 읽어요 to past tense?

Replace -어요 with -었어요 to get 읽었어요, meaning “(I) read a book on the subway.”

How do you express future tense?

Attach -을 거예요 to the stem: 읽을 거예요, meaning “(I) will read a book on the subway.”

How is 읽어요 pronounced in everyday speech?

Due to consonant assimilation, 읽어요 is pronounced roughly [일거요]. The final cluster ㄺ in 읽 simplifies to ㄹ before the vowel 어.

How can I make this sentence more formal or honorific?

Use the formal declarative ending -습니다:
“지하철에서 책을 읽습니다.”
To honor the subject explicitly, you could say 읽으십니다, but 읽습니다 is usually sufficient.

How would you say the same thing casually to a friend?

In 반말, change 읽어요 to 읽어:
“지하철에서 책을 읽어.”
In very casual speech you can even drop the object particle:
“지하철에서 책 읽어.”