Hacim hesabı raf ünitesini de içeriyor.

Because hacim hesabı is a very common Turkish noun-compound pattern.

• hacim = volume
• hesap = calculation/account
• hacim hesabı = volume calculation

In this pattern, the second noun usually takes the ending -(s)ı / -(s)i / -(s)u / -(s)ü. So hesap becomes hesabı.

There is also a sound change:

• hesap
  • vowel-initial ending → hesabı
• final p often becomes b before a vowel

So this is the same kind of change as:

• kitap → kitabı

Here, -ı is not the accusative ending. It is part of the compound form.

Not necessarily. In sentences like this, it is usually just a noun compound, not real possession.

So:

• hacim hesabı = volume calculation
• not literally its calculation of volume

Turkish uses this structure very often where English uses one noun before another:

• araba kapısı = car door
• mutfak masası = kitchen table
• hacim hesabı = volume calculation

So even though the form looks like a possessive ending, the meaning is often just a fixed noun+noun expression.

Because raf ünitesini is the direct object of the verb içeriyor, and it is a specific one, so it takes the accusative ending.

Base form:

• raf ünitesi = shelf unit

Object form:

• raf ünitesini = the shelf unit

What is happening step by step:

• ünite
• ünitesi = shelf unit
• ünitesini = the shelf unit, as a definite direct object

That final -ni appears because the noun already has the compound/possessive-type ending, so Turkish adds the accusative as -nı / -ni / -nu / -nü.

They do different jobs.

• -si is part of the noun compound: raf ünitesi
• -ni is the accusative marking on that whole noun phrase: raf ünitesini

So:

• raf ünitesi = shelf unit
• raf ünitesini = the shelf unit, as the thing being included

The n is a buffer consonant. Turkish often inserts buffer consonants when endings are added to avoid awkward vowel combinations.

Here de means also, too, or as well.

So:

• raf ünitesini de = the shelf unit too / also the shelf unit

It is written separately because this de is a separate particle, not a normal suffix.

A useful contrast:

• evde = in the house
• ev de = the house too

So in your sentence, de is not part of ünitesini. It is its own word, and it adds the meaning also.

Because de usually comes right after the word or phrase it emphasizes.

Here it follows raf ünitesini, so the meaning is roughly:

• the shelf unit too
• also the shelf unit

If you move de, the emphasis can change. Turkish is very sensitive to where words like de are placed.

Because the neutral Turkish word order is usually Subject + Object + Verb.

In this sentence:

• Hacim hesabı = subject
• raf ünitesini de = object phrase
• içeriyor = verb

So the structure is:

• Hacim hesabı / raf ünitesini de / içeriyor
• The volume calculation / also the shelf unit / includes

Turkish word order is more flexible than English, but putting the verb at the end is the most standard pattern.

Because the Turkish -iyor form is used more broadly than the English progressive.

• içeriyor literally has the -iyor ending
• but in natural English, the best translation here is usually includes

So even though -iyor is often taught as a present continuous form, Turkish uses it in many everyday statements where English prefers the simple present.

You could think of içeriyor here as:

• contains
• includes

The dictionary verb is içermek = to include / contain.

Turkish usually does not have articles like English a/an and the.

English has to choose an article, but Turkish often leaves that to context.

In this sentence, raf ünitesini is in the accusative, which strongly suggests a specific object, so English naturally says:

• the shelf unit

For hacim hesabı, English may say:

• the volume calculation
• or sometimes just volume calculation

depending on the situation. Turkish often leaves that kind of distinction unstated unless the context makes it clear.

Because Turkish often uses one noun directly before another noun, just like English does in expressions such as shelf unit or coffee cup.

So:

• raf = shelf
• raf ünitesi = shelf unit

The first noun often stays unchanged. This is a very normal Turkish pattern:

• çay bardağı = tea glass
• otobüs durağı = bus stop
• raf ünitesi = shelf unit

So raf is not behaving like an adjective here; it is a noun used to modify another noun.