هو متدرب جديد.

In Arabic, the verb to be is usually not expressed in the present tense.

So:

• هو متدرب جديد = He is a new trainee

There is no separate word for is here. This is called a nominal sentence in Arabic.

If you wanted the past tense, then Arabic would use a verb:

• كان متدربًا جديدًا = He was a new trainee

Word by word:

• هو = he
• متدرب = trainee
• جديد = new

So the full sentence is literally:

• He trainee new

But in natural English, that becomes:

• He is a new trainee

Yes, in many contexts you can say just متدرب جديد if it is clear from context who you mean.

However, هو is often included to make the subject explicit:

• هو متدرب جديد = He is a new trainee

Using هو can sound more complete, and it may also add a slight sense of contrast or emphasis, depending on context:

• هو متدرب جديد، وليس مديرًا = He is a new trainee, not a manager

So both are possible, but هو makes the sentence clearer on its own.

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

So:

• متدرب جديد = a new trainee

Literally:

• trainee new

This is the normal word order in Arabic noun phrases.

Because the meaning is a new trainee, not the new trainee.

In Arabic, indefiniteness is shown by the absence of ال (al-, the definite article the).

So:

• متدرب جديد = a new trainee
• المتدرب الجديد = the new trainee

A key rule is that the adjective matches the noun in definiteness:

• متدرب جديد = both indefinite
• المتدرب الجديد = both definite

جديد is the masculine singular form, and it matches متدرب, which is also masculine singular.

Arabic adjectives must agree with the nouns they describe in:

• gender
• number
• definiteness
• usually case as well

So for a female trainee, you would say:

• هي متدربة جديدة = She is a new trainee

Here:

• متدربة = feminine form of trainee
• جديدة = feminine form of new

متدرب is a noun meaning trainee. It comes from the verb تدرّب meaning to train or to undergo training.

The pattern متفعل often gives a meaning related to the person doing or undergoing the action. So متدرب is someone who is in training.

You can think of it as roughly similar to trained person / trainee / intern, depending on context.

In full formal Arabic grammar, yes, the sentence would be written with case endings:

• هو متدربٌ جديدٌ

Both متدربٌ and جديدٌ take ـٌ here because they are indefinite and in the nominative form.

However, in normal modern writing, short vowel endings are usually not written, so you commonly see:

• هو متدرب جديد

Both forms represent the same sentence.

You would say:

• هو المتدرب الجديد

Here, both the noun and the adjective become definite:

• المتدرب = the trainee
• الجديد = the new

This is an important rule in Arabic: if the noun is definite, the adjective must also be definite.

It is pronounced approximately:

• mu-ta-dar-rib

A few notes:

• مُ = mu
• تَ = ta
• درّ has a doubled r sound
• ب at the end is a clear b

And the whole sentence is approximately:

• huwa mutadarrib jadīd

The long ī in جديد should be held a little longer than a short vowel.