هو يتذكر اسم الطبيب، لكنني لا أتذكره الآن.

Yes, the verb form يتذكر already tells you the subject is he. So هو is not strictly necessary.

Arabic often drops subject pronouns when the verb already makes the subject clear. So you could also say:

يتذكر اسم الطبيب، لكنني لا أتذكره الآن.

Including هو adds clarity or emphasis, and here it also helps set up a contrast:

• هو يتذكر... = he remembers...
• لكنني... = but I do not remember...

So in this sentence, هو helps emphasize the contrast between he and I.

Both يتذكر and أتذكر are in the imperfect form, which often corresponds to the present tense in English.

Here they mean:

• يتذكر = he remembers / he is remembering
• أتذكر = I remember / I am remembering

In context, the natural translation is simple present:

• هو يتذكر = He remembers
• لا أتذكره الآن = I do not remember it now

The prefixes are important:

• يـ = he
• أ = I

So:

• يتذكر = he remembers
• أتذكر = I remember

This is because Arabic is using an idafa construction, often called a construct phrase.

اسم الطبيب literally means the name of the doctor.

In an idafa:

• the first noun usually does not take ال
• the second noun can be definite, and that makes the whole phrase definite

So:

• اسم طبيب = a doctor’s name / the name of a doctor
• اسم الطبيب = the doctor’s name

That is why اسم appears without ال, even though the whole phrase is definite.

Because the sentence means the doctor’s name, not a doctor’s name.

In the idafa phrase اسم الطبيب:

• اسم = name
• الطبيب = the doctor

Since الطبيب is definite, the whole phrase becomes definite:

• اسم الطبيب = the doctor’s name

If you removed الـ, the meaning would become more indefinite:

• اسم طبيب = a doctor’s name

لكنني is a common formal way to say but I...

It is built from لكنّ plus the pronoun -ني, and it is very natural in Modern Standard Arabic.

So:

• لكنني = but I
• لكني is also common as a spelling variant

You may sometimes hear or see لكن أنا, but لكنني is more standard and smoother in formal Arabic.

In this sentence:

• لكنني لا أتذكره الآن = but I do not remember it now

لا is the normal particle used to negate the present/imperfect verb in Modern Standard Arabic.

So:

• أتذكره = I remember it
• لا أتذكره = I do not remember it

This is the standard way to say a present negative statement.

The -ه means him/it, but here it means it.

It refers back to اسم الطبيب — specifically to اسم (name), which is a masculine singular noun. That is why the attached pronoun is -ه.

So:

• أتذكره = I remember it
• here it = the doctor’s name

Even though الطبيب means the doctor, the pronoun here refers to the name, not the doctor himself.

Because it agrees with the noun it refers to, which is اسم.

• اسم is masculine singular
• so the pronoun is -ه = it/him for masculine singular

This is a useful point: when a whole phrase like اسم الطبيب is referred to with a pronoun, the agreement is usually based on the head noun, which here is اسم.

Arabic often places time expressions like الآن (now) at the end of the sentence, and that sounds very natural here.

So:

• لا أتذكره الآن = I do not remember it now

You can sometimes move الآن for emphasis, but the end position is very common and straightforward.

For example:

• الآن لا أتذكره = Right now, I do not remember it
• لا أتذكره الآن = I do not remember it now

Both are possible, but the sentence you have is very natural.

Sometimes learners wonder about this because both verbs are related to memory and mention.

• تذكّر / يتذكر usually means to remember / recall
• ذكر / يذكر often means to mention, though in some contexts it can also relate to remembering

In this sentence, يتذكر is the clearer and more natural choice for remember.

So:

• هو يتذكر اسم الطبيب = He remembers the doctor’s name

Using يذكر here would more easily suggest mentioning rather than simply remembering.

A fully vocalized version would be:

هُوَ يَتَذَكَّرُ اسْمَ الطَّبِيبِ، لَكِنَّنِي لَا أَتَذَكَّرُهُ الْآنَ.

A few useful points:

• يَتَذَكَّرُ and أَتَذَكَّرُ end in ـُ because they are in the indicative mood
• اسْمَ has ـَ because it is the direct object of يتذكر
• الطَّبِيبِ has ـِ because it is the second noun in an idafa, which is in the genitive
• أَتَذَكَّرُهُ includes ـهُ = it
• الْآنَ is often written with a final fatHa in full vocalization

So the case relations are:

• اسمَ = accusative, as the thing remembered
• الطبيبِ = genitive, because of the idafa structure

Yes, absolutely.

You can say:

يتذكر اسم الطبيب، لكنني لا أتذكره الآن.

That is fully correct because يتذكر already tells you the subject is he.

So the difference is mainly one of style and emphasis:

• هو يتذكر... = slightly more explicit or contrastive
• يتذكر... = more economical and still perfectly normal

In this sentence, keeping هو helps emphasize the contrast with لكنني.