هذا العضو جديد.

Because Arabic usually does not use a present-tense verb meaning is/are/am in sentences like this.

So:

• هذا العضو جديد literally looks like this the-member new
• but it means This member is new

This kind of sentence is called a nominal sentence. In the present tense, Arabic simply puts the parts next to each other.

If you want a past or future meaning, then Arabic does use a verb, for example:

• كان هذا العضو جديدًا = This member was new
• سيكون هذا العضو جديدًا = This member will be new

هذا means this for a masculine singular noun.

In هذا العضو جديد:

• هذا = this
• العضو = the member
• جديد = new

So هذا العضو means this member.

Arabic commonly places the demonstrative before the noun in simple examples like this. So:

• هذا العضو = this member

Because عضو is masculine singular, هذا is the correct form.

After هذا, Arabic normally uses a definite noun when you mean this + noun in the sense of identifying a specific thing.

So:

• هذا العضو = this member

The الـ makes عضو definite: the member.

That may feel strange to an English speaker, because English says this member, not this the member. But in Arabic, this is normal.

Compare:

• هذا العضو جديد = This member is new
• هذا عضو جديد = This is a new member

So both forms exist, but they mean different things.

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

In other words:

• هذا العضو = the subject, this member
• جديد = what is being said about it, new

So جديد means is new, not the new.

This is a very important contrast:

• هذا العضو جديد = This member is new
• هذا العضو الجديد = this new member

In هذا العضو الجديد, الجديد is a regular adjective describing العضو, so it matches it in definiteness. In هذا العضو جديد, جديد is the predicate, so it does not take الـ.

Yes. It agrees in gender and number.

Since العضو is masculine singular, the predicate is:

• جديد = new (masculine singular)

If the noun were feminine singular, you would use:

• هذه العضوة جديدة = This female member is new

If it were plural, the form would change too, for example:

• هؤلاء الأعضاء جدد = These members are new

So even though جديد does not take الـ here, it still agrees with the noun in gender and number.

This is a very common question, and the difference is important.

1) هذا العضو جديد

This means:

• This member is new

Here, هذا العضو is a definite noun phrase: this member. Then جديد is the predicate: is new.

2) هذا عضو جديد

This means:

• This is a new member

Here, هذا stands more independently as this is... Then عضو جديد means a new member.

So:

• هذا العضو جديد = talking about a specific member, saying he/it is new
• هذا عضو جديد = identifying someone/something as a new member

With full case endings, it is:

• هٰذا العُضْوُ جَديدٌ

Usually, in normal Arabic writing for learners and in most everyday printed Arabic, those final short vowels are omitted, so you see:

• هذا العضو جديد

But in fully vocalized, formal grammar terms:

• هٰذا = demonstrative
• العُضْوُ ends with ـُ because it is the subject
• جَديدٌ ends with ـٌ because it is an indefinite predicate

A learner does not always need to pronounce every case ending in ordinary conversation, but it is useful to know they exist in formal MSA.

It is pronounced roughly:

• al-ʿuḍw(u)

A few notes:

• The الـ is fully pronounced here because ع is a moon letter, not a sun letter.
• The first consonant of عضو is ع (ʿayn), a sound English does not have.
• The ض is an emphatic consonant, often transliterated ḍ.
• The word ends in a consonant cluster-like shape -ḍw in careful pronunciation.

A simple learner-friendly transliteration of the whole sentence is:

• hādhā al-ʿuḍw jadīd

You can say it, but it does not mean the same thing.

• هذا العضو جديد = This member is new
• هذا العضو الجديد = this new member

So هذا العضو الجديد is a noun phrase, not the same complete statement.

It identifies which member you mean: the new one.

If you want a full sentence with that phrase, you could say something like:

• هذا العضو الجديد هنا = This new member is here

So the presence or absence of الـ on جديد changes the structure:

• جديد = predicate, is new
• الجديد = adjective, new as part of the new member

Yes, عضو is grammatically treated as masculine in this sentence, so the sentence uses:

• هذا
• جديد

If you want an explicitly feminine form, Modern Standard Arabic often uses:

• عضوة = female member

Then the sentence would be:

• هذه العضوة جديدة = This female member is new

Notice all three changes:

• هذا → هذه
• عضو → عضوة
• جديد → جديدة

This shows the normal feminine agreement pattern in Arabic.