هذا أول يوم في العمل.

In Arabic, the present-tense to be is usually not written or spoken in simple sentences like this.

So:

• هذا أول يوم في العمل
• literally: this first day at the-work
• naturally: This is the first day at work

This kind of sentence is called a nominal sentence. Arabic often says:

• هو طالب = He is a student
• الجو جميل = The weather is beautiful

No separate word for is is needed in the present tense.

هذا means this and is the masculine singular demonstrative.

It is used because يوم (day) is a masculine singular noun.

So:

• هذا = this (for masculine singular nouns)
• يوم = day (masculine)

If the noun were feminine, you would usually use هذه instead.

Example:

• هذه سيارة = This is a car

So in your sentence, هذا matches يوم.

Because أول means first, while واحد means one.

So:

• أول = first
• واحد = one

Arabic clearly distinguishes between:

• one day = يوم واحد
• the first day / first day = أول يوم

That is the same difference as English one vs first.

Both patterns exist in Arabic, but they are used a little differently.

In this sentence:

• أول يوم is a very natural way to say first day

Here, أول comes before the noun and forms a kind of fixed phrase with it.

Another possible expression:

• اليوم الأول = the first day

That form is also correct, but in a sentence like this, Arabic commonly uses:

• هذا أول يوم في العمل

A fuller alternative with a more explicit structure would be:

• هذا هو اليوم الأول في العمل
• This is the first day at work

So أول يوم is not wrong or incomplete—it is a normal, idiomatic way to express first day here.

Because in the phrase أول يوم, the noun after أول is normally left without الـ.

So Arabic says:

• أول يوم
• literally: first day

Even though English usually says the first day, Arabic does not need to make يوم definite here.

This is one of those places where Arabic and English do not match word-for-word.

So:

• English: the first day
• Arabic: أول يوم

That is perfectly normal.

في العمل literally means in the work, but in natural English it often means at work or on the job, depending on context.

Breakdown:

• في = in / at
• العمل = the work / work

Arabic often uses the definite article in places where English does not. So العمل here is very natural.

In this sentence, في العمل means something like:

• at work
• at the workplace
• on the job

So the whole sentence means the speaker is talking about someone's first day in a work setting.

Yes, the literal order is close to:

• this first day in the work

But that is just the Arabic structure. Natural English adds is and adjusts the phrasing:

• This is the first day at work

Arabic does not always match English word-for-word, especially in simple present-tense sentences.

A useful way to understand it is:

• هذا = topic: this
• أول يوم في العمل = comment: the first day at work

So the sentence structure is normal Arabic, even if it feels compressed compared to English.

In fully vocalized formal Arabic, the sentence would be:

• هٰذا أَوَّلُ يَوْمٍ فِي العَمَلِ

Here is why:

• أولُ ends in ـُ because it is the predicate of the sentence and is nominative
• يومٍ ends in ـٍ because it comes after أول in a construct-like relationship, so it is genitive
• العملِ ends in ـِ because it comes after the preposition في, and nouns after prepositions are genitive

In normal everyday writing, these short vowels are usually not written, so you just see:

• هذا أول يوم في العمل

A careful pronunciation is:

• hādhā awwalu yawmin fī l-ʿamali

In normal pause-style pronunciation, you will often hear something closer to:

• hādhā awwal yawm fī l-ʿamal

A few pronunciation notes:

• هذا = hādhā
• أول = awwal / awwalu
• يوم = yawm
• العمل = al-ʿamal

The ع in العمل is the letter ʿayn, which has no exact English equivalent.

Yes—demonstratives in Arabic must agree with the noun in gender and number.

In this sentence:

• هذا = masculine singular
• يوم = masculine singular

So they match correctly.

Compare:

• هذا كتاب = This is a book
  masculine singular

• هذه سيارة = This is a car
  feminine singular

So if the main noun were feminine, هذا would change to هذه.

Yes, depending on context, an English speaker might understand it that way.

في العمل most naturally suggests:

• at work
• in work
• on the job

So the most common translation is:

• This is the first day at work

But in some contexts, especially if you are talking generally about beginning a job, English might also phrase it as:

• This is the first day of work

The Arabic itself is broad enough that both can make sense, though at work is usually the most straightforward translation.

The sentence is perfectly good Modern Standard Arabic.

It is also simple enough that very similar wording could be understood easily in many everyday contexts. However, in actual spoken dialects, people often change small things such as pronunciation or wording.

As an MSA model sentence, though, it is natural and useful:

• هذا أول يوم في العمل

It is exactly the kind of sentence a learner should know.