kono siroi syatu ha kuroi zubon ni yoku aimasu.

この means this, and it must come directly before a noun phrase.

So:

• この 白い シャツ = this white shirt
• not 白い この シャツ

In Japanese, この attaches to the noun it is pointing out, even if an adjective comes in between in English. A good way to think of it is that この starts the whole noun phrase:

• この白いシャツ = this white shirt
• その黒いズボン = those/that black pants
• あの新しい店 = that new store over there

Japanese spacing here is just for learners. Normally it would be written as この白いシャツ.

白い and 黒い are い-adjectives.

• 白い = white
• 黒い = black

The -い is part of the adjective itself, not just an ending added for decoration. In Japanese, い-adjectives can directly modify nouns:

• 白いシャツ = a white shirt
• 黒いズボン = black pants

This is different from English, where adjectives do not change form.

Also, not all color words behave the same way. For example:

• 白い, 黒い, 赤い, 青い are common い-adjectives
• but colors like ピンク often use の or act differently depending on context

The particle は marks the topic of the sentence: what the sentence is about.

So in:

• この白いシャツは黒いズボンによく合います。

the topic is:

• この白いシャツは = as for this white shirt...

The rest of the sentence says something about that shirt:

• 黒いズボンによく合います = it goes well with black pants

English often starts directly with the subject, but Japanese frequently uses は to introduce the topic instead.

Here, に marks the thing that something matches or goes well with.

So:

• 黒いズボンに合う = to match black pants
• 黒いズボンによく合う = to go well with black pants

With 合う / 合います in the sense of to suit / to match, Japanese often uses に for the item something matches.

So the shirt is the topic, and 黒いズボンに shows what it matches.

Sometimes yes, but the nuance can differ a little.

Common patterns include:

• A は B に合う = A matches B
• A と B は合う = A and B go well together

In your sentence:

• この白いシャツは黒いズボンによく合います。

the focus is on the shirt and how it matches the black pants.

If you used と, it might sound more like describing the two items as a pair:

• この白いシャツと黒いズボンはよく合います。
• This white shirt and black pants go well together.

So both can work, but に fits the original sentence very naturally.

Here, よく means well, not often.

So:

• よく合います = matches well / goes well together

This is a very common point of confusion because よく can mean different things depending on context:

• 日本語をよく勉強します。 = I study Japanese a lot/often.
• この色はあの色によく合う。 = This color goes well with that color.

In this sentence, because it is used with 合います, the meaning is clearly well.

In this sentence, 合います means to match, to go well with, or to suit.

The dictionary form is:

• 合う

The polite form is:

• 合います

Important: 合う has several meanings in Japanese depending on context. It can mean things like:

• to fit
• to suit
• to match
• to be in harmony with

Here, because the sentence is about clothing and colors, the meaning is to match / go well with.

Because Japanese normally puts the main verb at the end.

So the structure is roughly:

• この白いシャツは = as for this white shirt
• 黒いズボンに = with black pants
• よく = well
• 合います = matches

A very literal order might be:

• This white shirt, black pants with, well matches.

That sounds unnatural in English, but it is normal in Japanese.

It can be either, depending on context.

Japanese nouns usually do not change form for singular and plural the way English nouns do.

So ズボン can mean:

• pants
• a pair of pants
• sometimes trousers

In English, we usually translate it as pants or trousers.

The sentence does not need to mark plural explicitly because the meaning is already clear from context.

Because ズボン is just the normal Japanese noun for trousers/pants. Japanese nouns do not work like English count nouns.

In English, pants is grammatically plural even when talking about one item of clothing. Japanese does not copy that pattern. It simply uses the noun ズボン.

So:

• 黒いズボン = black pants / a pair of black pants

The Japanese word itself does not show singular vs. plural the way English does.

シャツ is a broad loanword from English shirt, but in Japanese it often refers to a collared shirt or a shirt-like top depending on context.

In everyday use, it can be fairly general, but context matters. For example:

• Tシャツ = T-shirt
• ワイシャツ = dress shirt / business shirt

So 白いシャツ here most naturally sounds like a white shirt, probably not a T-shirt unless the context says so.

Because Japanese often omits things that are understood from context.

In English, we would usually say:

• This white shirt goes well with black pants.

In Japanese, once この白いシャツ is established as the topic with は, there is no need to add a separate word like it.

Japanese frequently leaves out pronouns when they are obvious.

It can be grammatical, but the nuance changes.

• は makes this white shirt the topic: As for this white shirt, it goes well with black pants.
• が tends to identify or emphasize the subject more strongly.

So:

• この白いシャツは黒いズボンによく合います。 = A natural general statement about the shirt.

• この白いシャツが黒いズボンによく合います。 = This white shirt is the one that goes well with black pants.

The が version can sound more contrastive or selective, as if choosing this shirt among several possibilities.

Yes. 合います is the polite -ます form.

Compare:

• 合う = plain form
• 合います = polite form

So this sentence is appropriate in normal conversation, in shops, when speaking politely, and in many everyday situations.

A plain version would be:

• この白いシャツは黒いズボンによく合う。

That sounds more casual.

No. Standard Japanese is normally written without spaces:

• この白いシャツは黒いズボンによく合います。

The spaces in your example are only there to help learners see the parts more easily.

This is very common in teaching materials, especially for beginners.