التكاليف كبيرة، لا سيما فاتورة المرافق.

Because التكاليف is a non-human plural, and in Modern Standard Arabic, non-human plurals are very often treated grammatically as feminine singular.

So:

• التكاليف = costs / expenses (plural)
• كبيرة = big / high / considerable (feminine singular)

This is completely normal in Arabic.

A similar pattern:

• الكتب مفيدة = The books are useful
• السيارات سريعة = The cars are fast

Even though books and cars are plural, the adjective often appears in the feminine singular form.

لا سيما is an expression meaning:

• especially
• particularly
• not least

So in this sentence, it highlights one item as a special example:

• التكاليف كبيرة، لا سيما فاتورة المرافق.
• The costs are high, especially the utilities bill.

It is a fairly formal expression and is common in written Arabic.

Because the speaker is singling out one particular thing as an example: the utilities bill.

So the meaning is:

• The costs are high, especially the utilities bill.

If the speaker wanted to emphasize multiple bills, they could use a plural instead, such as:

• لا سيما فواتير المرافق = especially the utility bills

But here, فاتورة is singular because one bill is being highlighted.

This is an iḍāfa construction, often called a genitive/possessive construction.

It consists of:

• فاتورة = bill
• المرافق = utilities / facilities

Together:

• فاتورة المرافق = the utilities bill / the bill for utilities

Important iḍāfa rules:

1. The first noun usually does not take ال.
2. The second noun can be definite with ال.
3. The whole phrase becomes definite if the second noun is definite.

So:

• فاتورة المرافق = the utilities bill not just a utilities bill

In this context, المرافق usually means utilities or utility services, such as:

• electricity
• water
• gas
• sometimes internet or similar services, depending on context

The singular مرفق often means facility, amenity, or utility/service.
The plural مرافق can mean:

• facilities
• amenities
• utilities

In فاتورة المرافق, the intended meaning is usually utilities.

Arabic often uses nominal sentences in the present tense, with no explicit verb for “to be.”

So:

• التكاليف كبيرة literally looks like:
• The costs high

But in natural English, it means:

• The costs are high

This is one of the most important differences between Arabic and English:

• Present-tense is / am / are is usually not written in Arabic nominal sentences.

الـ is the definite article, meaning the.

So:

• تكاليف = costs
• التكاليف = the costs

In this sentence, the speaker is talking about a known or specific set of costs, not costs in general.

This is because of the iḍāfa structure.

In an iḍāfa:

• the first noun usually appears without الـ
• the second noun determines whether the whole phrase is definite

So:

• فاتورة مرافق = a utilities bill / bill of utilities (indefinite-sounding)
• فاتورة المرافق = the utilities bill (definite)

Even without الـ on فاتورة, the whole phrase is definite because المرافق is definite.

The singular is تكلفة.

So:

• تكلفة = cost / expense
• تكاليف = costs / expenses

This is a broken plural, which means the plural is formed by changing the internal pattern of the word, not just by adding a regular ending.

A simple pronunciation guide is:

• at-takālīf kabīrah, lā siyyamā fātūrat al-marāfiq

A few notes:

• التكاليف is pronounced at-takālīf, because ت is a sun letter, so the l of الـ assimilates.
• المرافق is pronounced al-marāfiq, because م is a moon letter, so the l is pronounced normally.

Yes. Common alternatives include:

• خصوصًا
• وخاصةً

So you could also say:

• التكاليف كبيرة، خصوصًا فاتورة المرافق.
• التكاليف كبيرة، وخاصةً فاتورة المرافق.

These are also natural.
Very roughly:

• لا سيما = a bit more formal/literary
• خصوصًا = very common and straightforward
• وخاصةً = also common and natural

The comma separates the main statement from the phrase that adds emphasis.

Structure:

• التكاليف كبيرة = main statement
• لا سيما فاتورة المرافق = emphasizing one important example

So the comma works much like it would in English:

• The costs are high, especially the utilities bill.

Arabic punctuation often follows similar logic to English in modern writing, even though usage can vary a bit by writer or publication.