kanozyo no hyouzyou wo mireba, hitome de genki ga nai to wakaru.

If you look at her expression, you can tell at a glance that she isn’t well.

Breakdown of kanozyo no hyouzyou wo mireba, hitome de genki ga nai to wakaru.

• を: direct object particle
• が: subject particle
• の: possessive case particle
• と: quotative particle
• ない: not exist/have
• 〜ば: conditional form
• 見みる: to look
• 彼女かのじょ: she
• 一目ひとめ で: at a glance
• 元気げんき: well; energetic
• 表情ひょうじょう: facial expression
• 分わかる: to understand; to tell

Questions & Answers about kanozyo no hyouzyou wo mireba, hitome de genki ga nai to wakaru.

Why is の used in 彼女の表情? Is it possession?

Yes. の links nouns, and here it’s a possessive/attributive relationship: 彼女の表情 = her facial expression (the expression that belongs to/characterizes her). The same pattern works with many nouns, e.g. 私の名前 (my name), 友だちの家 (a friend’s house).

What nuance does 表情 have compared to 顔?

表情（ひょうじょう） means facial expression (the “look” on someone’s face—emotion, mood, etc.). 顔（かお） is the face as an object/body part.
So 表情を見る focuses on the emotional signal, while 顔を見る can be more literal (looking at someone’s face) and doesn’t automatically imply reading emotion.

Why is を used after 表情?

を marks the direct object of the verb 見る. In 表情を見れば, the thing being looked at is 表情.
So the structure is: [object] を 見る = look at [object].

How does 見れば work grammatically?

見れば is the ば-conditional form of 見る:

• dictionary: 見る
• conditional: 見れば

It commonly expresses: if/when you look (at it), then ... and often implies a general result or natural consequence. Here: If you look at her expression, you can tell...

Could this be 見たら or 見ると instead? What’s the difference?

Yes, and the nuance shifts slightly:

• 見れば: general condition/result; somewhat explanatory: if you look, you’ll understand.
• 見たら: “when/if you look (and then)” with a more event-like feel; can sound more specific to a situation.
• 見ると: often used for an automatic/inevitable result discovered upon doing the action: When I looked, I found that... / Look and you’ll see that...

All can work, but 見れば fits a general statement well.

What does 一目で mean, and why is で used?

一目（ひとめ） means one look / a glance. 一目で means at a glance / with one look.
The particle で here indicates the means or extent: you can tell by/with one glance. It’s similar to:

• 一瞬で (in an instant)
• この方法で (by this method)

Why is 元気がない used instead of 元気じゃない?

Both can mean not energetic / not well, but:

• 元気がない literally means (someone) has no energy and is a very common, natural way to describe someone seeming down, tired, or unwell.
• 元気じゃない is also valid, a more direct negation of 元気だ, and can feel a bit more conversational/blunt depending on context.

In this sentence, 元気がない sounds especially natural for “she doesn’t seem well/cheerful.”

What is the role of と in 元気がないと分かる?

と marks the content of what you understand/realize.
Pattern: [clause] と 分かる／思う／言う
So 元気がないと分かる = understand that she isn’t well / realize that she has no energy.

Why does Japanese use 分かる (intransitive) instead of something like “I understand” explicitly?

分かる often functions like it becomes clear / one can tell / I can tell, and Japanese frequently omits the subject when it’s obvious.
So while English often requires I can tell, Japanese can naturally say 分かる without stating 私は.

Is the subject of 分かる the speaker, or “anyone”?

It’s intentionally broad and can be read as anyone (in general) or the speaker/observer. The ば-conditional plus 分かる commonly creates a general statement: If you look, you can tell. Context decides whether it’s truly general or about the speaker’s viewpoint.

Could 彼女の表情を見れば be replaced by 彼女の表情を見るだけで?

Yes, and it changes the feel:

• 見れば: if/when you look
• 見るだけで: just by looking (no more is needed)

見るだけで一目で together can be redundant because both imply minimal effort/one glance. Typically you’d choose one emphasis:

• 表情を見れば、一目で分かる。
• 表情を見るだけで分かる。
• 一目で分かる。

Why is there a comma 、 after 見れば?

It separates the conditional clause from the main clause, similar to English:
If you look at her expression, you can tell at a glance...
Japanese writing often uses 、 to improve readability, especially after conditionals like 〜れば, 〜たら, 〜と, 〜ので, etc.

What’s the overall grammar structure of the sentence?

It’s basically:

• 彼女の表情を見れば = conditional clause (if/when you look at her expression)
• 一目で = adverbial phrase (at a glance)
• 元気がない = embedded clause (she has no energy / she isn’t well)
• と分かる = main predicate (you can tell / it’s clear that...)

So: [Condition], [adverb], [content] と分かる.