kounou wo yomu.

It is read こうのう.

In this kind of sentence, 効能 usually means something like efficacy, benefits, or medicinal effects. You often see it on medicine, supplements, cosmetics, or product descriptions.

を marks the direct object of the verb.

So in 効能を読む, the thing being read is 効能. In other words:

• 効能 = the thing you read
• 読む = to read

A very literal breakdown is read the efficacy/benefits information.

This is a standard feature of modern Japanese pronunciation.

The particle is written を, but in normal modern speech it is pronounced お. So:

• 効能を読む
• pronounced: こうのう を よむ
• actual sound: こうのう お よむ

Learners usually still refer to it as the を particle, even though its pronunciation is basically お.

読む is the plain, dictionary form of the verb.

Japanese often uses the plain form in:

• dictionary entries
• headings
• short written instructions
• casual speech
• example sentences

If you wanted a more polite full sentence, you could say:

• 効能を読みます。

Both are grammatically fine. The difference is mainly style and politeness.

Yes. This is standard Japanese word order.

Japanese typically puts the verb at the end, so:

• 効能 = object
• を = object marker
• 読む = verb

This object + を + verb pattern is extremely common in Japanese.

They are similar, but not identical.

• 効能 often refers to a product's stated efficacy or beneficial properties, especially for medicine, health products, or cosmetics.
• 効果 is a broader word meaning effect or result.

For example:

• 薬の効能 = the medicinal benefits / indications of a medicine
• 薬の効果 = the effect the medicine actually has

So 効能 can sound a bit more like the listed or recognized benefits of something.

It is understandable, but by itself it can sound a little context-dependent.

In real Japanese, people might also say things like:

• 説明を読む = read the explanation
• 成分や効能を読む = read the ingredients and benefits
• 効能を確認する = check the efficacy/benefits
• 効能書きを読む = read the label or description of the effects

So 効能を読む is not wrong, but it feels a little short and may depend on the context, such as reading a medicine label or product packaging.

Japanese often leaves the subject out when it is clear from context.

So 効能を読む。 could mean:

• I read the efficacy information
• You read the efficacy information
• Read the efficacy information

The exact subject is not stated, and Japanese often works that way. Context tells you who is doing the action.

Normally, Japanese is not written with spaces like this.

A natural written version would be:

• 効能を読む。

Spaces are often added in teaching materials to help learners see the parts more clearly:

• 効能
• を
• 読む

So the spaces are for readability, not standard Japanese spelling.

No. 読む is used for reading many kinds of written information, not just books.

You can read:

• 本 = a book
• 新聞 = a newspaper
• メール = an email
• 説明 = an explanation
• ラベル = a label
• 効能 = efficacy/benefits information

So using 読む with product information is completely normal.