هذه مكالمة مهمة.

Yes. هذه means this for a feminine singular noun.

In هذه مكالمة مهمة, the noun مكالمة (call / phone call) is grammatically feminine, so Arabic uses هذه, not هذا.

• هذا = this with a masculine singular noun
• هذه = this with a feminine singular noun

So:

• هذا كتاب = This is a book
• هذه مكالمة = This is a call

It is grammatically feminine because it ends in ة (called taa marbuuTa / tāʾ marbūṭa), which is a very common sign of feminine nouns in Arabic.

So مكالمة is treated as feminine in grammar, even though a call does not have biological gender in English.

Because of that, anything agreeing with it must also be feminine:

• هذه = feminine this
• مهمة = feminine important

Because adjectives in Arabic must agree with the noun they describe.

Here, مهمة describes مكالمة, so it matches it in:

• gender: feminine
• number: singular
• definiteness: indefinite

So:

• مكالمة = a call
• مهمة = important

Together: مكالمة مهمة = an important call

If the noun were masculine, the adjective would also be masculine:

• كتاب مهم = an important book

In Arabic, adjectives normally come after the noun they describe.

So Arabic says:

• مكالمة مهمة = literally call important

This is the standard pattern:

• بيت كبير = a big house
• سيارة جديدة = a new car
• مكالمة مهمة = an important call

So even though English puts the adjective first, Arabic usually puts it second.

In Arabic, in simple present-tense sentences like this one, the verb to be is usually not stated.

So هذه مكالمة مهمة literally looks like:

• this important call

but it means:

• This is an important call

This is very normal in Arabic. The present-tense is / am / are is usually understood from context.

Compare:

• أنا طالب = I am a student
• هذه سيارة = This is a car
• هذه مكالمة مهمة = This is an important call

Because the sentence means This is an important call, not This is the important call.

Both مكالمة and مهمة are indefinite here.

• مكالمة = a call
• مهمة = important (indefinite adjective matching an indefinite noun)

If you wanted the important call, you would make both the noun and adjective definite:

• المكالمة المهمة = the important call

In Arabic, when a noun is definite and has an adjective, the adjective also becomes definite.

Yes. هذه المكالمة مهمة means:

• This call is important

That is slightly different from:

• هذه مكالمة مهمة = This is an important call

The difference is:

• هذه مكالمة مهمة introduces something as an important call
• هذه المكالمة مهمة talks about this specific call and says it is important

So the presence of ال changes the meaning.

In fully vocalized MSA, it would usually be:

هٰذِهِ مُكَالَمَةٌ مُهِمَّةٌ

The ـٌ endings show that مكالمة and مهمة are indefinite nominative.

In everyday writing, these short vowels are usually omitted, so you normally see:

هذه مكالمة مهمة

Both are the same sentence; the second is just the usual unvocalized spelling.

هذه is usually pronounced haadhihi or hādhihi in careful MSA pronunciation.

A helpful breakdown:

• ها = hā
• ذِ = dhi
• هِ = hi

So: hā-dhi-hi

In slower, formal reading, you may hear all the vowels clearly. In faster speech, pronunciation can sound a little lighter depending on the speaker.

It is pronounced roughly mukālama in pause, or mukālamatun with full case ending in careful formal reading.

A simple breakdown:

• مُ = mu
• كا = kā
• لَ = la
• مَة = ma / mah at the end, depending on context

Important point: the final ة is usually pronounced like -a in pause.

So in normal citation form:

• مكالمة ≈ mukālama

This is a nominal sentence in Arabic, meaning a sentence built without a present-tense verb.

A simple way to analyze it is:

• هذه = the topic / demonstrative (this)
• مكالمة مهمة = what is being said about it

You do not need to know advanced grammar to use it correctly, but it helps to recognize that Arabic often forms present-tense statements this way.

Usually مكالمة most naturally means call, often specifically a phone call depending on context.

In many real situations, هذه مكالمة مهمة would be understood as:

• This is an important call
• or This is an important phone call

The exact English wording depends on context, but call is a good general translation.

The root is ك ل م which is related to speech or speaking.

مكالمة comes from a derived pattern that gives the sense of conversation / speaking with someone, so it often means:

• a call
• a conversation
• especially a phone call in modern usage

Knowing roots is useful because it helps you connect words such as:

• كلام = speech, talk
• تكلم = he spoke
• مكالمة = call / conversation

Yes. هامة is another word that can mean important.

So both can work:

• هذه مكالمة مهمة
• هذه مكالمة هامة

In many contexts, مهم / مهمة is more common in everyday modern usage, but both are correct MSA.

You would change both the demonstrative and the adjective to masculine.

For example:

• هذا كتاب مهم = This is an important book

Compare:

• هذه مكالمة مهمة = feminine noun
• هذا كتاب مهم = masculine noun

So Arabic agreement affects more than one word in the sentence.