okuba ga itai desu.

奥歯 (おくば) means a back tooth, usually a molar. It is more specific than just 歯 (tooth/teeth).

• 奥 = back, inner part
• 歯 = tooth

So the sentence is talking about pain in a tooth toward the back of the mouth, not just any tooth.

In Japanese, things like pain, ability, and feelings are often expressed with が.

So in 奥歯が痛いです, が marks the thing that is painful.

A useful pattern is:

• X が 痛い = X hurts / X is painful

This is different from English, where we might think of I as the subject: My back tooth hurts.
In Japanese, the focus is more like: As for the painful thing, it is the back tooth.

Yes, 痛い is an i-adjective. It means painful or hurting.

Japanese often uses adjectives where English uses verbs. So although English says My tooth hurts, Japanese says something closer to The back tooth is painful.

This is completely normal Japanese.

Common body-related expressions work the same way:

• 頭が痛い = My head hurts
• お腹が痛い = My stomach hurts
• 喉が痛い = My throat hurts

です makes the sentence polite.

• 奥歯が痛い。 = casual
• 奥歯が痛いです。 = polite

Even though 痛い is an adjective, it can still be followed by です in modern Japanese polite speech.

So here, です does not mean is by itself. It mainly adds politeness.

Yes, but the nuance changes.

• 奥歯が痛いです = neutral statement; the back tooth hurts
• 奥歯は痛いです = as for the back tooth, it hurts; this can sound contrastive or topical

Using は may suggest a comparison, such as:

• 奥歯は痛いですが、前歯は大丈夫です。
  • The back tooth hurts, but the front teeth are okay.

If you are simply reporting a symptom, が is usually the most natural choice.

Japanese often leaves out information that is obvious from context.

If you say 奥歯が痛いです, people normally understand that you mean my back tooth hurts, especially if you are talking about your own condition.

Japanese often omits possessives like my, your, or his when they are clear.

If you need to make it explicit, you can:

• 私の奥歯が痛いです。 = My back tooth hurts.

But in many everyday situations, that sounds less natural than simply saying 奥歯が痛いです.

Yes, it is natural and correct.

That said, in real conversation, people often make it a little more specific:

• 右の奥歯が痛いです。 = My back tooth on the right hurts.
• 左の奥歯が痛いです。 = My back tooth on the left hurts.
• 下の奥歯が痛いです。 = My lower back tooth hurts.

You might also hear:

• 奥歯が痛いんです。

The んです form sounds a bit more explanatory, like My back tooth hurts, you see / that's the problem. This is very common when explaining symptoms.

You can, because 痛む is a verb meaning to ache / to hurt, but 奥歯が痛いです is the more common and straightforward way to describe a symptom.

Compare:

• 奥歯が痛いです。 = My back tooth hurts.
• 奥歯が痛みます。 = My back tooth aches / hurts.

The 痛い version is very common in everyday speech.
The 痛む version is also correct, but may sound a bit more descriptive or situational depending on context.

For a beginner, X が 痛いです is the safest pattern to learn first.

It is pronounced おくば (okuba).

A learner may expect おくは because 歯 by itself is は, but in compounds it often changes sound:

• 歯 alone: は
• 奥歯: おくば
• 前歯: まえば
• 入れ歯: いれば

This kind of sound change is very common in Japanese compounds.

No. Normal Japanese writing does not use spaces like that.

It would usually be written as:

• 奥歯が痛いです。

Spaces are often added only in beginner materials to make the parts easier to see.

Because 痛い is an i-adjective, it changes like other i-adjectives.

Common forms:

• 奥歯が痛いです。 = My back tooth hurts.
• 奥歯が痛くないです。 = My back tooth does not hurt.
• 奥歯が痛かったです。 = My back tooth hurt.
• 奥歯が痛くなかったです。 = My back tooth did not hurt.

In very polite or careful Japanese, you may also see:

• 奥歯が痛くありません。
• 奥歯が痛くありませんでした。

These are good forms to know, especially in formal situations.