haguki ha akai desu.

It is usually read:

はぐき は あかい です。
Haguki wa akai desu.

A few pronunciation notes:

• 歯茎 = はぐき (haguki), meaning gums
• The particle は is written ha but pronounced wa
• 赤い = あかい (akai), meaning red
• です = desu, though in natural speech the u is often very light

So the full sentence sounds like:

haguki wa akai desu

When は is used as the topic particle, it is pronounced wa.

So in this sentence:

• 歯茎 = gums
• は = topic marker, pronounced wa

This is a very common beginner point in Japanese. The same character は has two roles:

• as a normal syllable in a word: pronounced ha
• as a particle: pronounced wa

So here, 歯茎は is read haguki wa.

は marks the topic of the sentence.

So 歯茎は赤いです。 literally has a structure like:

• As for the gums, they are red.

In more natural English, that becomes:

• The gums are red.

Japanese often organizes sentences as topic + comment:

• 歯茎は = as for the gums
• 赤いです = are red

So は tells you what the sentence is about.

Because 赤い is an -い adjective, and it directly describes something as red.

• 赤い = red
• 赤 = red as a noun, like the color red

With body parts or visible conditions, 赤い is the natural choice:

• 歯茎は赤いです。 = The gums are red.

If you said 赤です, that would sound more like identifying something’s color in a general way, such as:

• 車は赤です。 = The car is red.

But for something like inflamed gums, 赤い is the more natural descriptive form.

They can.

You can say:

• 歯茎は赤い。 = plain style
• 歯茎は赤いです。 = polite style

So 赤い already works as the predicate, and です is added for politeness.

This is standard modern Japanese. A useful beginner rule is:

• -い adjectives can end a sentence on their own
• adding です makes the sentence polite

Compare:

• 高い。 = It is expensive/tall.
• 高いです。 = It is expensive/tall. (polite)

One thing you should not do is add だ after an -い adjective:

• 赤いだ ✘

That is incorrect.

You often could, but the nuance changes.

• 歯茎は赤いです。 = As for the gums, they are red.
• 歯茎が赤いです。 = The gums are red / It’s the gums that are red.

Very roughly:

• は presents gums as the topic
• が highlights gums more specifically as the thing that is red

A common way to think about it:

• は is more like speaking about X
• が is more like X is the one that...

If someone asked:

• どこが赤いですか。 = What is red?

Then 歯茎が赤いです。 would feel very natural.

If you are simply making a statement about the gums in general, 歯茎は赤いです。 is also fine.

Yes, it is grammatically natural and understandable.

That said, in real-life situations, the choice between は and が depends on context.

For example, if a dentist is describing a symptom, 歯茎が赤いです。 may sound slightly more natural because it focuses on the specific thing that is red.

But 歯茎は赤いです。 is still a perfectly normal sentence, especially for learning basic sentence structure.

So the key point is:

• grammatically correct: yes
• natural: yes
• context may slightly favor が in some situations

Japanese nouns usually do not show singular vs. plural the way English does.

So 歯茎 can refer to:

• a gum area
• the gums in general
• the relevant person’s gums

Japanese often leaves number unmarked unless it matters.

This is very normal. English requires you to choose between gum and gums, but Japanese usually does not.

The listener understands from context.

Because Japanese often leaves that kind of information unstated if it is already clear from context.

For example, in a dentist’s office:

• 歯茎は赤いです。 might naturally mean Your gums are red.
• If someone is talking about their own condition, it might mean My gums are red.

Japanese frequently omits:

• subjects
• possessives
• other information that the listener can infer

So a bare noun like 歯茎 often means the relevant gums in the situation.

Yes. In a sentence about a body part, 赤い often suggests reddened, not just literally red as a color category.

So here it may imply:

• irritation
• inflammation
• abnormal redness

This is similar to English, where the gums are red often suggests a medical condition, not just a neutral color description.

So even though 赤い simply means red, the context can give it a more specific meaning.