tubasa ha siroi.

Because when は is used as the topic particle, it is pronounced wa, not ha.

So in 翼は白い, you read it as:

つばさ は しろい
with は sounding like wa

This is a special pronunciation used only for the particle. When は is part of a normal word, it is usually pronounced ha.

は marks 翼 as the topic of the sentence.

A helpful way to think about it is:

• As for wings, they are white
• Speaking of wings, they are white

It does not exactly equal English is. Instead, it tells you what the sentence is about, and then 白い gives information about that topic.

Because 白い is an i-adjective, and it needs the い to function as an adjective in this form.

• 白 by itself is not the normal standalone adjective form here
• 白い means white

Japanese adjectives are not used the same way as English adjectives. In this sentence, 白い works like a complete predicate, so 翼は白い is a full sentence.

Japanese often does not need a separate verb like English is when an i-adjective is the predicate.

So:

• 翼は白い = The wings are white
• literally, something like As for wings, white

This is normal Japanese grammar. With i-adjectives, the adjective itself can complete the sentence.

It can be either, depending on context.

Japanese nouns usually do not show singular/plural the way English does. So 翼 could mean:

• a wing
• wings

The listener figures it out from the situation.

Here it is usually read つばさ.

So the whole sentence is:

つばさはしろい。

Depending on the level of the material, you may also see spacing added for learners:

つばさ は しろい。

Because 白い can already end the sentence by itself.

• 翼は白い。 is plain style
• 翼は白いです。 is polite style

Both are grammatical. The version without です is more casual or plain, and is often the dictionary-style form you see in textbooks.

Yes, but the nuance changes.

• 翼は白い。 = As for the wings, they are white
• 翼が白い。 = The wings are the ones that are white or It is the wings that are white

Very roughly:

• は introduces the topic
• が can sound more specific, identifying, or focused

At a beginner level, it is enough to know that は is the more neutral topic-marking choice here.

In this sentence, 白い is the main predicate.

That means the structure is:

• 翼 = topic
• は = topic marker
• 白い = what is being said about the topic

If you wanted white wings as a noun phrase, you would say:

白い翼

There, 白い directly modifies 翼.

But in 翼は白い, it is not just describing a noun inside a phrase. It is finishing the whole sentence.

The spaces are usually just for learners.

Normal Japanese is typically written without spaces:

翼は白い。

Textbooks and beginner materials often insert spaces to make the structure easier to see.

Yes, it can.

The word 翼 can sound a little more literary or elevated than a very everyday concrete noun, especially depending on context. A sentence like 翼は白い。 could appear in ordinary language, but it can also feel poetic if it is talking about birds, angels, symbolism, or imagery.

So the grammar is basic, but the impression of the sentence may vary with context.