هذا خبر مهم عن الطقس.

In Modern Standard Arabic, the verb to be is usually not stated in the present tense.

So:

• هذا خبر مهم عن الطقس = This is important news about the weather

Arabic simply puts the parts of the sentence together without a present-tense is.

But in the past or future, Arabic does use a verb:

• كان هذا خبرًا مهمًا = This was important news
• سيكون هذا خبرًا مهمًا = This will be important news

هذا means this.

In this sentence, it points to something masculine and singular:

• هذا = this
• هذه = this for feminine nouns

Since خبر is masculine singular, هذا is the correct form here.

Because خبر is a masculine singular noun.

In Arabic, demonstratives must match the gender of the noun they refer to.

• هذا خبر = This is news / This is a report
• هذه رسالة = This is a message

So the sentence uses هذا because خبر is masculine.

This is a very common question.

There is an important difference between:

• هذا خبر مهم = This is important news
• هذا الخبر مهم = This news / this report is important

In هذا خبر مهم, خبر is indefinite, so it works like the predicate: This is important news.

In هذا الخبر مهم, الخبر is definite, and now the phrase means this news/report as a specific item.

So both are correct Arabic, but they mean slightly different things.

This is a nominal sentence.

A nominal sentence in Arabic often begins with a noun, pronoun, or demonstrative like هذا, and it does not need a present-tense verb to be.

Here the sentence is built like this:

• هذا = this
• خبر مهم = important news
• عن الطقس = about the weather

So the whole structure is a normal Arabic present-tense statement.

Because مهم is an adjective, and in Arabic adjectives normally come after the noun they describe.

So:

• خبر مهم = important news

not the other way around.

This is the normal Arabic order:

• noun + adjective

Examples:

• كتاب جديد = a new book
• بيت كبير = a big house
• خبر مهم = important news

Arabic adjectives must agree with the noun they describe in:

• gender
• number
• definiteness
• and, in fully vocalized Arabic, case

Here:

• خبر is masculine singular and indefinite
• so مهم is also masculine singular and indefinite

That is why you get:

• خبر مهم

If the noun were definite, the adjective would also become definite:

• الخبر المهم = the important news/report

عن is a preposition that often means:

• about
• concerning
• regarding

So:

• عن الطقس = about the weather

It connects the noun خبر with the topic being talked about.

Because the sentence means the weather, not just weather in a general or indefinite sense.

• الطقس = the weather

In Arabic, many abstract or general ideas are often expressed with ال when English might or might not use the depending on context.

Here عن الطقس is the natural way to say about the weather.

In spelling, it is الطقس, but in pronunciation the ل of ال is absorbed because ط is a sun letter.

So it is pronounced approximately:

• aṭ-ṭaqs

not fully al-taqs.

The spelling does not change, but the pronunciation does.

This is a very common feature of Arabic pronunciation with the definite article ال.

Yes, in fully vocalized Modern Standard Arabic, the sentence would be:

• هذا خبرٌ مهمٌّ عن الطقسِ

The endings are:

• خبرٌ — nominative
• مهمٌّ — nominative, matching خبر
• الطقسِ — genitive, because it comes after the preposition عن

In normal everyday writing, these short vowel endings are usually omitted, so you often just see:

• هذا خبر مهم عن الطقس

Because عن is a preposition, and prepositions in Arabic make the following noun genitive.

So:

• عن الطقسِ

The final -i sound is the genitive ending.

This happens with many prepositions, for example:

• في البيتِ = in the house
• من المدرسةِ = from the school
• عن الطقسِ = about the weather

خبر is singular.

It often means:

• news
• a piece of news
• a report
• an item of news

Its plural is:

• أخبار = news items / reports

This can feel different from English because news in English is grammatically singular but refers to information in general. In Arabic, خبر is a normal singular countable noun.

That is less natural.

The most natural order is:

• هذا خبر مهم عن الطقس

because مهم directly describes خبر, so it should usually come right after it:

• خبر مهم = important news

Then the prepositional phrase comes after that:

• عن الطقس = about the weather

So for a learner, the best pattern to remember is:

• demonstrative + noun + adjective + prepositional phrase

A careful MSA reading would be approximately:

• hādhā khabarun muhimmun ʿani ṭ-ṭaqsi

Without case endings, many learners read it more simply as:

• hādhā khabar muhim ʿan iṭ-ṭaqs

A few pronunciation notes:

• هذا = hādhā
• خبر = khabar
• مهم = muhimm
• عن = ʿan
• الطقس = pronounced aṭ-ṭaqs / iṭ-ṭaqs depending on connection in speech

The most important thing is to remember that الطقس is pronounced with an absorbed l because of ط.