عجلة القيادة جديدة.

Because Arabic usually does not use a present-tense copula in simple sentences like this.

So:

• عجلة القيادة جديدة.
• literally: The steering wheel new
• natural English: The steering wheel is new

This is called a nominal sentence in Arabic. In the present tense, Arabic normally leaves out is / am / are.

If you wanted a past-tense version, then Arabic would use a verb, for example:

• كانت عجلة القيادة جديدة.
• The steering wheel was new.

It is an iḍāfa (إضافة), often called a construct phrase.

That means it works like:

• X of Y
• or sometimes an English compound noun

So:

• عجلة = wheel
• القيادة = driving / steering
• عجلة القيادة = the wheel of driving, which is the natural Arabic way to say the steering wheel

This is very common in Arabic. Another example is:

• باب البيت = the door of the house = the house door

Because in an iḍāfa, the first noun normally does not take ال.

So Arabic marks definiteness differently here:

• عجلة القيادة = the steering wheel
• not العجلة القيادة

The whole phrase becomes definite because the second noun is definite:

• القيادة = the driving / the steering

In other words, in an iḍāfa:

• first noun: usually no ال
• second noun: can carry definiteness
• the whole phrase can still mean the ...

Because it agrees with عجلة, which is a feminine singular noun.

In Arabic, adjectives usually agree with the noun they describe in:

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

So here:

• عجلة = feminine singular
• جديدة = feminine singular

The masculine form would be:

• جديد = new
• feminine: جديدة

Because here جديدة is the predicate of the sentence, not an adjective inside the noun phrase.

The sentence structure is:

• عجلة القيادة = the steering wheel
• جديدة = is new

So جديدة means new as the information being stated about the subject.

Compare these:

• عجلة القيادة جديدة. = The steering wheel is new.
• عجلة القيادة الجديدة = the new steering wheel

That second one is a noun phrase, not a full sentence. There, الجديدة is an adjective directly modifying عجلة القيادة, so it must match in definiteness.

With full case endings, it would be:

• عَجَلَةُ القِيادَةِ جَديدَةٌ

Why?

• عجلةُ is nominative because it is the subject of a nominal sentence
• القيادةِ is genitive because it is the second term of the iḍāfa
• جديدةٌ is nominative because it is the predicate

In normal modern writing, these short vowels are usually omitted, so you usually see:

• عجلة القيادة جديدة

A careful full reading is approximately:

• ʿajalatu l-qiyādati jadīdatun

In normal pause, many learners will hear something closer to:

• ʿajlat al-qiyāda jadīda

A few helpful pronunciation notes:

• ع is the Arabic letter ʿayn, which has no exact English equivalent
• ق in القيادة is q, a deeper sound than English k
• جديدة is jadīda

Great question. The letter ة (tāʾ marbūṭa) behaves differently depending on position.

In عجلة القيادة, the word عجلة is followed by another word in an iḍāfa, so the ة is pronounced like t:

• ʿajlat al-qiyāda

But at the end of the sentence, جديدة is usually pronounced with an -a sound in pause:

• jadīda

So:

• عجلة in connection: often -at / -t
• جديدة at the end in pause: usually -a

It is a complete sentence.

Specifically, it is a nominal sentence:

• عجلة القيادة = the subject
• جديدة = the predicate

So it means a full thought:

• The steering wheel is new.

If it were just a phrase meaning the new steering wheel, it would be:

• عجلة القيادة الجديدة

That is not a full sentence by itself.

Literally, القيادة comes from a root related to leading / driving.

Depending on context, it can mean things like:

• driving
• leadership
• guidance/steering in certain expressions

In عجلة القيادة, it gives the sense of steering, so the whole phrase means:

• steering wheel

This is one of those cases where the literal structure and the natural English translation are a little different.

Yes, but the basic order here is the most straightforward and neutral one.

Normal order:

• عجلة القيادة جديدة.
• The steering wheel is new.

Arabic can sometimes move parts of a sentence around for emphasis, but for learners, this version is the best one to use and understand first.

So the safest takeaway is:

• subject first
• predicate second

That gives the natural simple meaning.