getuyou no asa ha densya ga tokuni komimasu.

Because 月曜の朝 means Monday morning as one noun phrase.

• 月曜 = Monday
• 朝 = morning
• の links them, like Monday's morning or more naturally Monday morning

Using に would not work here because に marks a specific time when something happens, while の is connecting two nouns.

So:

• 月曜の朝 = Monday morning
• 月曜に = on Monday

If you wanted, you could also say something like:

• 月曜の朝に電車は特に混みます

  But in the given sentence, 月曜の朝 is being treated as the topic, so の is the natural choice.

Here, の connects two nouns.

It shows that 朝 is the morning belonging to or associated with 月曜. In English, we usually translate this kind of の very naturally:

• 日本の車 = Japanese cars / cars of Japan
• 春の雨 = spring rain
• 月曜の朝 = Monday morning

So の is doing a basic noun-linking job.

The は marks 月曜の朝 as the topic of the sentence.

So the sentence is structured like:

• As for Monday mornings, trains are especially crowded.

This is a very common Japanese pattern:

• X は Y です
• As for X, Y

Here:

• 月曜の朝は = as for Monday mornings
• 電車が特に混みます = trains are especially crowded

So は is not just marking time; it is setting the scene or topic for what follows.

Because the sentence has two different functions being marked:

• 月曜の朝は = the topic
• 電車が = the thing that has the property especially crowded

In other words:

• As for Monday mornings, it is trains that are especially crowded.

Using が here highlights 電車 as the subject within the comment about the topic.

If you said 電車は, the nuance would shift a bit. It could still be grammatical in some contexts, but the original sentence naturally divides into:

1. topic: Monday mornings
2. subject of the statement: trains

That is why は and が appear together.

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

So 電車 can mean:

• a train
• trains
• the train
• trains in general

The meaning depends on context.

In this sentence, it clearly means trains in general, not one specific train. That is why English usually translates it as trains.

This is very common:

• 猫が好きです = I like cats
• 車が多いです = There are a lot of cars

Even though the Japanese noun does not change form, the English translation often needs a plural.

特に means especially or particularly.

It modifies the verb 混みます and tells you that the crowdedness is not just ordinary—it is noticeable or stronger than usual.

So:

• 電車が混みます = trains are crowded
• 電車が特に混みます = trains are especially crowded

Its placement before the verb is very normal in Japanese. Adverbs often go before the part they modify.

Other examples:

• とても暑いです = it is very hot
• よく食べます = eat often
• 特に混みます = are especially crowded

Both can be used, but they have slightly different feel.

• 混みます often describes a general tendency or repeated situation.
• 混んでいます often describes the current state of being crowded, though it can also be used more generally depending on context.

In this sentence, the speaker is talking about a habitual fact:

• Monday mornings are the time when trains tend to be especially crowded.

So 混みます fits well because it sounds like a general pattern.

Compare:

• この電車は今混んでいます。 = This train is crowded now.
• 月曜の朝は電車が特に混みます。 = On Monday mornings, trains are especially crowded.

Yes.

• 月曜 = Monday
• 月曜日 = Monday

Both are correct. 月曜 is simply shorter and a little more casual or compact.

In everyday speech and writing, both are common. The shorter weekday forms are used a lot:

• 月曜 = Monday
• 火曜 = Tuesday
• 水曜 = Wednesday

So you could also say:

• 月曜日の朝は電車が特に混みます。

That would mean the same thing.

The dictionary form of the verb is 混む or 込む, read こむ.

In this context, 混む is the usual spelling when it means to be crowded.

Its ます-form is:

• 混む → 混みます

This is a u-verb pattern:

• 読む → 読みます
• 書く → 書きます
• 混む → 混みます

So the む changes to み before ます.

Not usually. The Japanese sentence sounds more general than that.

Because 電車 is not clearly singular here, the natural meaning is:

• Trains are especially crowded on Monday mornings
• or The trains are especially crowded on Monday mornings

If the speaker meant one specific train, the context would usually make that clearer, for example:

• この電車は月曜の朝に特に混みます。
  • This train is especially crowded on Monday mornings.

So in the original sentence, 電車 is best understood as trains in general.

It normally means Monday mornings in general.

That is because:

• 月曜の朝は is a general time-topic
• 混みます suggests a repeated or habitual situation

So the sentence describes a regular pattern, not a one-time event.

If the speaker wanted to talk about one particular Monday morning, they would usually add more context, such as:

• 今朝は = this morning
• 先週の月曜の朝は = last Monday morning
• その月曜の朝は = that Monday morning

Without that kind of detail, the sentence is understood as a general statement.