هذا منتصف الطريق.

It is a nominal sentence in Arabic, not a verbal sentence.

• هذا = this
• منتصف الطريق = the middle of the road / the midpoint of the way

So the structure is:

• هذا = the subject/topic
• منتصف الطريق = the predicate/comment

Arabic often builds simple X is Y sentences this way, with no separate present-tense verb.

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

So:

• هذا منتصف الطريق literally looks like this middle the-road but naturally means This is the middle of the road or This is the halfway point.

If you wanted a past-tense version, then Arabic would use a verb such as كان.

هذا means this for a masculine singular noun.

It is masculine here because the thing being identified is منتصف (middle / midpoint), and منتصف is masculine.

Even though الطريق is often treated as feminine in Arabic, that does not control the demonstrative here, because الطريق is inside the phrase منتصف الطريق. The main noun of that phrase is منتصف.

It is an iḍāfa construction, often called a genitive construction or annexation.

This is a very common Arabic pattern:

• first noun + second noun
• often equivalent to X of Y in English

So:

• منتصف الطريق = middle of the road
• more literally: midpoint of the road

In an iḍāfa:

• the first noun usually does not take ال
• the second noun can make the whole phrase definite

Because it is the first part of an iḍāfa.

In Arabic, the first noun in an iḍāfa normally does not take ال. So:

• منتصف الطريق = correct
• المنتصف الطريق = not correct in standard Arabic for this meaning

Even without ال on منتصف, the whole phrase can still be definite because the second noun is definite.

Because الطريق is definite: the road / the way.

In the iḍāfa منتصف الطريق, the definiteness of the second noun makes the whole phrase definite:

• طريق = a road / a way
• الطريق = the road / the way
• منتصف الطريق = the middle of the road

So the phrase refers to a specific middle point, not just a middle of a road.

In careful spelling it is written الطريق, but in pronunciation the ل of ال is assimilated because ط is a sun letter.

So it is pronounced:

• aṭ-ṭarīq

not:

• al-ṭarīq

This is why you may hear the ṭ sound doubled.

A common pronunciation in normal reading is:

• hādhā muntaṣaf aṭ-ṭarīq

If full case endings are pronounced in formal Arabic, it would be:

• hādhā muntaṣafu ṭ-ṭarīqi

A rough breakdown:

• هذا = hādhā
• منتصف = muntaṣaf
• الطريق = aṭ-ṭarīq

With full case endings, it is:

• هٰذا مُنْتَصَفُ الطَّرِيقِ

Here is why:

• هذا is essentially fixed in form
• منتصفُ is nominative because it is the predicate of the nominal sentence
• الطريقِ is genitive because it is the second noun in the iḍāfa

So:

• منتصفُ = -u
• الطريقِ = -i

They are related, but not exactly the same.

• منتصف الطريق = the middle of the road / the midpoint / halfway point
• نصف الطريق = half of the road / half the way

In many contexts, both may be translated as halfway, but:

• منتصف focuses more on the middle point
• نصف focuses more on half

So منتصف الطريق often sounds a bit more like the midpoint.

Yes. That is possible.

• هذا منتصف الطريق = simple, normal, direct
• هذا هو منتصف الطريق = more emphatic, like This is the midpoint

The word هو here is not exactly a normal translated he. In this kind of sentence, it can act as a separator pronoun for emphasis and clarity.

Both are correct, but the shorter version is very natural.

Here it is a noun.

It means something like:

• middle
• midpoint
• center point in this context

So منتصف الطريق is a noun phrase, not an adjective phrase.

That is why the sentence works like:

• This
  • the midpoint of the road

rather than:

• This
  • middle

Sometimes, yes, depending on context.

A very literal translation is:

• This is the middle of the road or
• This is the midpoint of the way

But in natural English, if the context is progress, distance, or a journey, it could also be understood as:

• This is halfway
• This is the halfway point

So the exact English wording depends on context, even though the Arabic structure stays the same.