بالتأكيد يضبط أخصائي البصريات وسادة الأنف وإطار النظارة.

بالتأكيد means certainly, definitely, or of course.

Literally, it is something like with certainty:

• بـ = with/by
• تأكيد = confirmation, certainty, emphasis

So this is a very common Arabic way to make the sentence sound more confident or emphatic. In fully vocalized Arabic, the noun after بـ is genitive, so you would have بالتأكيدِ.

This is normal Arabic word order.

A very common pattern in Modern Standard Arabic is:

• verb + subject + object

So after the adverbial expression بالتأكيد, the sentence continues as a verbal sentence:

• يضبط = adjusts
• أخصائي البصريات = the optician / optical specialist

You could also say:

• أخصائي البصريات يضبط...

That version is also correct, but it feels more subject-focused. The original version is a very natural neutral verbal sentence.

Here يضبط means adjusts.

The verb comes from ضبط, which can mean things like:

• to adjust
• to regulate
• to set correctly
• to make precise

In this sentence, adjusts is the best translation.

Its form also tells you grammatical information:

• يـ at the beginning marks 3rd person masculine singular in the imperfect/present
• so يضبط means he adjusts / he is adjusting, depending on context

Because Arabic verbs already include person/gender/number information, you do not need a separate word for he.

Literally, أخصائي البصريات means specialist of optics or specialist in optometry/optics.

Breakdown:

• أخصائي = specialist
• البصريات = optics / optometry / optical science

In natural English, this is often rendered as optician or sometimes optometry specialist, depending on context.

A learner may notice that البصريات looks plural because of ـات. That is normal: in Arabic, words with this ending can also refer to a field or discipline, not just a simple plural.

Because أخصائي البصريات is an iḍāfa construction, also called a construct phrase.

In an iḍāfa:

• the first noun usually does not take الـ
• the second noun determines whether the whole phrase is definite or indefinite

So:

• أخصائي البصريات = the specialist of optics = the optician

Even though أخصائي has no الـ, the whole phrase is definite because البصريات is definite.

Both of these are also iḍāfa constructions.

They work like this:

• وسادة الأنف

  • literally: pad of the nose
  • natural English: nose pad

• إطار النظارة

  • literally: frame of the glasses
  • natural English: the glasses frame or the frame of the glasses

In Arabic, this noun + noun structure is extremely common. The second noun specifies what kind of thing the first noun is.

Again, this is because of iḍāfa.

In Arabic, the first noun in an iḍāfa normally does not take الـ:

• وسادة الأنف
• إطار النظارة

But the whole phrase can still be definite because the second noun is definite:

• الأنف
• النظارة

So Arabic expresses definiteness differently from English here. English says the nose pad or the glasses frame, while Arabic uses the construct phrase without الـ on the first noun.

Because Arabic and English package this idea differently.

In Arabic, نظارة can refer to a pair of glasses. So even though English commonly uses the plural-looking word glasses, Arabic often uses a singular noun for the item.

So:

• إطار النظارة = the frame of the glasses / the glasses frame

This is completely normal in Arabic and does not mean only one lens or one side.

In this phrase, it is pronounced as t.

That is a very common rule:

• when a word with ة stands alone at the end, it is usually pronounced like -a or -ah
• but when it is followed by another word in an iḍāfa, the ة is pronounced t

So:

• وسادة by itself: ends like -a(h)
• وسادة الأنف: the ة is pronounced t

This is one of the most important pronunciation rules for ة.

That is just a structural difference between the two languages.

Arabic often uses a full noun phrase in an iḍāfa:

• وسادة الأنف = literally pad of the nose
• إطار النظارة = literally frame of the glasses

English often turns the first part into a noun modifier instead:

• nose pad
• glasses frame

So the Arabic is not strange; it is simply using its normal noun-linking pattern.

Because normal Arabic writing usually leaves short vowels and case endings unwritten.

Under the surface, the grammar is roughly:

• أخصائي البصريات = the subject, so it is nominative
• وسادة الأنف and إطار النظارة = the direct objects, so their first nouns are accusative
• the second noun in each iḍāfa is genitive

In carefully vowelled Arabic, these endings would be shown, but in ordinary print they are usually omitted. That is why learners often have to infer the grammar from word order and sentence structure rather than from visible endings alone.