seigenzikan ha mizikai.

It is read:

せいげんじかん は みじかい。

• 制限時間 = せいげんじかん = time limit
• は is written ha but pronounced wa when it is the topic particle
• 短い = みじかい = short

When は is used as a particle, it is pronounced wa.

So in this sentence:

• 制限時間は = As for the time limit, ...

But when は is part of a word, it is usually pronounced ha.

This is one of the first pronunciation exceptions learners meet in Japanese.

は marks the topic of the sentence.

So 制限時間は短い literally feels like:

• As for the time limit, it is short.

That is why the sentence does not sound exactly like a word-for-word English sentence. Japanese often presents a topic first, then comments on it.

In Japanese, a sentence with an i-adjective like 短い does not need a separate word for is in the present tense.

So:

• 短い can mean is short

That means:

• 制限時間は短い = The time limit is short

This is normal Japanese grammar.

短い is the full dictionary form of the adjective short.

It is an i-adjective, so it already works as a predicate by itself.

• plain form: 短い
• polite form: 短いです

So:

• 制限時間は短い。 = plain style
• 制限時間は短いです。 = polite style

You cannot just say 短 by itself here.

Yes. 短い is an i-adjective.

Japanese adjectives are often divided into two main types:

• i-adjectives: end in -い, like 短い, 高い, 暑い
• na-adjectives: like 静か, 便利

Since 短い is an i-adjective, it can directly end the sentence:

• 制限時間は短い。

Sometimes yes, but the nuance changes.

• 制限時間は短い。 = As for the time limit, it is short.
• 制限時間が短い。 = The time limit is what is short / It is the time limit that is short

Very roughly:

• は = topic, more general statement
• が = subject, often more focused or contrastive depending on context

For a simple neutral statement, は is very natural.

The basic order is:

topic + comment

So:

• 制限時間 = topic noun
• は = topic marker
• 短い = comment/predicate

Japanese often puts the main description at the end, so the adjective comes last here.

This sentence is in plain style because it ends with 短い.

• plain: 制限時間は短い。
• polite: 制限時間は短いです。

The plain form is not automatically rude. It is commonly used in:

• writing
• statements
• casual conversation
• headings or instructions

Yes.

• 制限 = restriction / limit
• 時間 = time

Together, 制限時間 means time limit.

This is a very common kind of Japanese compound noun: two kanji words combine into one more specific term.

Japanese is normally written without spaces:

• 制限時間は短い。

Spaces are often added in teaching materials to make sentence structure easier for learners to see.

So the spaced version is helpful for study, but the natural written form is the version without spaces.

Yes, depending on context.

The core meaning is simply that the time limit is short, but natural English translations can vary:

• The time limit is short.
• The allotted time is short.
• There isn’t much time allowed.

Japanese often leaves some interpretation to context, so several English versions can fit the same sentence.

Because 短い is an i-adjective, it changes like this:

• present: 短い = is short
• negative: 短くない = is not short
• past: 短かった = was short
• past negative: 短くなかった = was not short

So you could say:

• 制限時間は短くない。 = The time limit is not short.
• 制限時間は短かった。 = The time limit was short.