التطعيم عند الطبيب البيطري اليوم.

Because Arabic often leaves out is / am / are in present-tense nominal sentences.

So التطعيم عند الطبيب البيطري اليوم is understood as something like:

• The vaccination is at the veterinarian today
• or The vaccination appointment is at the vet today

This is completely normal in Modern Standard Arabic.
If you wanted past or future, you would usually add a verb, such as كان for was.

It can work as a full sentence, but it also has the feel of a short schedule entry or reminder.

Arabic often allows very compact sentences, especially when the context is clear. So this could sound like:

• a reminder
• a calendar note
• a short announcement

A fuller version might be:

• موعد التطيم عند الطبيب البيطري اليوم = The vaccination appointment is at the veterinarian today
• or التطعيم يكون عند الطبيب البيطري اليوم in a more explicit style

But the original is perfectly natural as a short statement.

No, التطعيم is a noun, not a verb.

It is a verbal noun, often called a maṣdar, from a verb related to vaccinating or inoculating. In this sentence it means the vaccination or the immunization.

So the sentence does not say to vaccinate.
It refers to the event or procedure itself.

The الـ makes the noun definite.

So:

• تطعيم = vaccination / a vaccination
• التطعيم = the vaccination

In this sentence, the speaker is most likely referring to a specific, known vaccination, such as an appointment already being discussed.

Here, عند means something like:

• at
• with
• at the place of
• in the care of

So عند الطبيب البيطري means at the veterinarian's or with the veterinarian.

This is very common with people, especially professionals:

• عند الطبيب = at the doctor's
• عند الأستاذ = with the teacher
• عند الصيدلي = at the pharmacist's

It is not always exactly the same as في, which usually means in or inside a place.

Because in Arabic, the noun comes first and the adjective comes after it.

So:

• الطبيب = the doctor
• البيطري = veterinary

Together:

• الطبيب البيطري = the veterinary doctor = the veterinarian

This is the normal Arabic order.
English says veterinary doctor, but Arabic says doctor veterinary.

Because Arabic adjectives must match the noun they describe in definiteness.

Since الطبيب is definite, the adjective must also be definite:

• طبيب بيطري = a veterinary doctor
• الطبيب البيطري = the veterinary doctor / the veterinarian

This matching is very important in Arabic adjective phrases.

Here it is an adjective describing الطبيب.

So literally, it means veterinary.
But the whole phrase الطبيب البيطري functions as a noun phrase meaning the veterinarian.

English often uses a special profession word, while Arabic builds it more transparently as the doctor + veterinary.

اليوم means today, and here it functions as a time expression.

It tells you when the vaccination is happening.

So the structure is roughly:

• التطعيم = topic
• عند الطبيب البيطري = where / with whom
• اليوم = when

Arabic often places time expressions flexibly, so you could also hear other word orders depending on emphasis.

Yes. Arabic word order is often flexible, especially with adverbs of time.

For example, you could also say:

• اليوم التطعيم عند الطبيب البيطري
• التطعيم اليوم عند الطبيب البيطري

These versions are all understandable, but the emphasis changes slightly.

The original التطعيم عند الطبيب البيطري اليوم sounds natural and straightforward, especially as a reminder or schedule-like statement.

In fully inflected formal Arabic, it would typically be read something like:

• التطعيمُ عندَ الطبيبِ البيطريِّ اليومَ

A simple breakdown:

• التطعيمُ: nominative, because it is the main topic or subject of the nominal sentence
• عندَ: an adverbial word meaning at/with
• الطبيبِ: genitive after عند
• البيطريِّ: also genitive, because it follows الطبيب as an adjective
• اليومَ: accusative as an adverb of time

In everyday pronunciation, especially outside careful formal reading, these final case endings are often not pronounced.

This is a good pronunciation question because the الـ is not always pronounced the same way.

In:

• التطعيم
• الطبيب

the first main consonants are ت and ط, which are sun letters. That means the l sound of الـ is not pronounced, and the next consonant is doubled.

So they are pronounced approximately like:

• at-taṭʿīm
• aṭ-ṭabīb

But in البيطري, the letter ب is a moon letter, so the l is pronounced:

• al-bayṭarī

So the three words are pronounced roughly:

• at-taṭʿīm
• ʿinda aṭ-ṭabīb al-bayṭarī
• al-yawm

Its most direct meaning is with / at the veterinarian.

Depending on context, English may naturally translate it as:

• at the vet
• with the vet
• at the veterinarian's office

So even though the Arabic literally mentions the person, English may refer to the place.

If you specifically wanted to say at the veterinary clinic, Arabic could also use something like:

• في العيادة البيطرية

But the original sentence naturally suggests the veterinarian as the relevant person or location.