يظن المسؤول الممارسة مهمة.

A natural breakdown is:

• يظن — the verb: he thinks / he considers
• المسؤول — the subject: the official
• الممارسة — the first object
• مهمة — the second object / complement

So the structure is:

• verb + subject + object 1 + object 2

This happens because ظنّ is one of the Arabic verbs that can take two objects, similar to English consider in a sentence like The official considers practice important.

Because ظنّ belongs to a group often called verbs of thinking or judging. These verbs can connect:

1. the thing being judged, and
2. the judgment about it.

So in this sentence:

• الممارسة = the thing being judged
• مهمة = the judgment about it

In English, we do something similar:

• He considers practice important
• She finds the task difficult

Arabic uses the same kind of pattern with ظنّ.

Because مهمة here is not an ordinary attributive adjective inside a noun phrase. It is a predicate-like complement telling us what the official thinks about الممارسة.

Compare:

• الممارسة المهمة = the important practice
  Here المهمة is a regular adjective describing the noun directly.

• يظن المسؤول الممارسة مهمة = The official thinks practice is important
  Here مهمة means important, not the important one.

So مهمة is indefinite because it functions more like the predicate in practice is important.

Formally, مهمة is an adjective meaning important.

But in this sentence, it is being used in a complement position after the first object. So syntactically, it is the second object of ظنّ, while semantically it describes الممارسة.

So you can think of it as:

• an adjective in form
• a second object/complement in function

This is very common in Arabic.

With full case endings, the sentence would be:

يَظُنُّ الْمَسْؤُولُ الْمُمَارَسَةَ مُهِمَّةً

The cases are:

• الْمَسْؤُولُ — nominative (-u) because it is the subject
• الْمُمَارَسَةَ — accusative (-a) because it is the first object
• مُهِمَّةً — accusative (-an) because it is the second object

In normal Arabic writing, these short vowels are usually omitted, so learners have to infer the grammar from structure and vocabulary.

Because the subject is المسؤول, which is masculine singular.

So the verb appears in the masculine singular form:

• يظن = he thinks

If الممارسة were the subject, the verb would normally be feminine singular:

• تظن الممارسة...

So the masculine verb helps confirm that المسؤول is the subject here.

Yes. A very common alternative is:

يظن المسؤول أن الممارسة مهمة

This means essentially the same thing:
The official thinks that practice is important.

The difference is mainly structural:

• يظن المسؤول الممارسة مهمة
  uses the two-object pattern of ظنّ

• يظن المسؤول أن الممارسة مهمة
  uses a full subordinate clause: that practice is important

Both are correct, but the first one is especially useful for learning how ظنّ works grammatically.

No. Here الممارسة is a noun.

It comes from the root related to مارس and functions as a verbal noun or abstract noun, meaning something like practice / exercising / engaging in an activity depending on context.

In this sentence, it behaves just like any other noun:

• it has ال
• it receives accusative case
• it serves as the first object of يظن

So even though its meaning is connected to an action, grammatically it is a noun here.

Yes. Arabic word order is flexible.

You could also say:

المسؤول يظن الممارسة مهمة

This puts the subject first. The meaning stays basically the same.

The original sentence begins with the verb, which is very common in Arabic:

• Verb–Subject–Object/Complement

The alternative is:

• Subject–Verb–Object/Complement

In fully vocalized Arabic, case endings make the roles clear. In unvocalized Arabic, word order and context help a lot.

Because it matches الممارسة in gender and number.

• الممارسة is feminine singular
• مهمة is also feminine singular

That agreement shows that مهمة is the quality being assigned to الممارسة.

If the first object were masculine, the complement would normally be masculine too. So this agreement helps the learner see the connection between the two words.

It is pronounced approximately:

al-masʾūl

A helpful breakdown is:

• mas
• then a small glottal stop for ء
• then ūl

So not masool smoothly, but more like mas-'ool.

The hamza in مسؤول is important in careful pronunciation, even though many learners find it tricky at first.