الحقيقة مهمة.

A careful pausal pronunciation is:

al-ḥaqīqa muhimma

If you read it with full classical case endings, it is:

al-ḥaqīqatu muhimmatun

A few pronunciation notes:

• ح in الحقيقة is a deeper, breathier h than English h
• ق is a deep q sound, not an English k
• the final ة in both words is usually pronounced like -a / -ah when you stop at the word

So in everyday reading aloud, learners often say al-ḥaqīqa muhimma.

Because Arabic often leaves out the present-tense verb to be.

So الحقيقة مهمة literally looks like:

• the truth
• important

But it naturally means Truth is important or The truth is important.

This is called a nominal sentence in Arabic. In the present tense, Arabic usually does not say is / am / are.

Compare:

• الحقيقة مهمة = truth is important
• كانت الحقيقة مهمة = truth was important

It is a basic nominal sentence made of:

• الحقيقة = the subject/topic
• مهمة = the predicate/comment

In traditional Arabic grammar terms:

• الحقيقة is the مبتدأ
• مهمة is the خبر

So the structure is:

[subject] + [predicate]

which is one of the most common sentence patterns in Arabic.

ال is the Arabic definite article, like the in English.

So حقيقة means something like truth / a truth, while الحقيقة means the truth.

However, with abstract nouns, Arabic often uses ال where English may simply use the bare noun. That is why الحقيقة can be translated naturally as either:

• the truth
• truth

depending on context.

Because الحقيقة is grammatically feminine, and Arabic adjectives must agree with the nouns they describe.

So:

• مهم = important (masculine)
• مهمة = important (feminine)

Since الحقيقة is feminine, the predicate must also be feminine:

• الحقيقة مهمة

This agreement is very important in Arabic.

One big clue is the ending ة in حقيقة.

That ending, called tāʾ marbūṭa, very often marks feminine nouns.

So:

• حقيقة is feminine
• therefore the adjective/predicate must also be feminine: مهمة

This is why الحقيقة مهم would be incorrect in standard Arabic.

Because in this kind of sentence, the predicate is usually indefinite.

So:

• الحقيقة مهمة = the truth is important

Here مهمة is not the important; it is simply describing the subject.

This is different from:

• الحقيقة المهمة

That means the important truth, where المهمة is an adjective directly modifying الحقيقة inside a noun phrase.

So the difference is:

• الحقيقة مهمة = Truth is important.
• الحقيقة المهمة = the important truth

In fully vowelled formal Arabic, yes:

• الحقيقةُ
• مهمةٌ

Both are in the nominative case, because in a basic nominal sentence both the مبتدأ and the خبر are nominative.

But in normal modern writing, those short vowels are usually not written, so you will commonly just see:

الحقيقة مهمة

Also, when pausing at the end of words, speakers usually do not pronounce the full case endings.

The normal beginner-friendly order is:

الحقيقة مهمة

That is the most neutral way to say it.

Arabic can sometimes move the predicate first for emphasis in formal style, but beginners should be careful, because without case endings the result can become confusing or look like a different structure.

So the safest choice is:

• الحقيقة مهمة

Use that as your standard pattern until you are comfortable with word order and case.

Here it means important, so it is functioning as an adjective/predicate.

But the same spelling مهمة can also be a noun meaning mission or task.

Context tells you which meaning is intended.

In this sentence:

• الحقيقة مهمة

it clearly means important, because it is describing الحقيقة.

So even though مهمة can be a noun in other sentences, here it is best understood as the feminine form of important.