الموعد يوم الاتنين.

Because Arabic often leaves out the verb to be in the present tense.

So الموعد يوم الاتنين is literally something like:

• the appointment — Monday day
• natural English: The appointment is on Monday

This is very normal in both Standard Arabic and Egyptian Arabic. If you want past or future, then a verb can appear, but in simple present statements like this, no is is needed.

It is a very common Arabic sentence type: topic + comment.

• الموعد = the appointment
• يوم الاتنين = on Monday / Monday

So:

• الموعد is what you are talking about
• يوم الاتنين tells you when it is

You can think of it as an Arabic nominal sentence: The appointment — on Monday.

يوم means day, and in Egyptian Arabic it is very common to say يوم + day of the week when talking about when something happens.

So:

• يوم الاتنين = Monday / on Monday

This is a very natural everyday way to express the day of an event.

English uses on Monday, but Arabic often uses يوم الاتنين instead.

Because يوم الاتنين acts like an iḍāfa structure, also called a construct phrase.

In this kind of phrase:

• the first word usually does not take ال
• the second word can be definite

So:

• يوم الاتنين = the day of Monday / Monday

That is why you get يوم الاتنين, not اليوم الاتنين.

Also, be careful: اليوم usually means today, so اليوم الاتنين would not mean the same thing.

In Arabic, days of the week are usually treated as definite words, so they commonly appear with ال.

For example:

• الاتنين = Monday
• التلات = Tuesday
• الأربع = Wednesday

So in يوم الاتنين, the weekday itself naturally keeps ال.

الاتنين is the Egyptian Arabic spelling, reflecting how people commonly say it in speech.

The Standard Arabic form is:

• الاثنين

In Egyptian Arabic, the ث sound is very often pronounced like ت, so:

• الاثنين becomes الاتنين in everyday writing and speech

Both are connected, but الاتنين is the more colloquial Egyptian form.

A rough pronunciation is:

il-moʿed yōm il-itnēn

A few notes:

• ال is often pronounced il or el
• الاتنين is commonly said as il-itnēn
• pronunciation varies a bit by speaker and region

If you are aiming for natural Egyptian speech, the most important part is recognizing and producing الاتنين as the everyday Egyptian form of Monday.

Sometimes people may understand it, but الموعد يوم الاتنين is clearer and more natural.

Using يوم makes the time expression sound complete and idiomatic. For a learner, it is a very good pattern to copy:

• الموعد يوم الاتنين
• الدرس يوم التلات
• الفرح يوم الجمعة

So yes, you may hear shorter expressions in fast speech, but يوم is a safe and natural choice.

Arabic often does not need a preposition in time expressions where English uses on.

So instead of saying:

• on Monday

Arabic can simply say:

• يوم الاتنين

This is one of those places where Arabic and English package meaning differently. The idea of on is already understood from the time expression itself.

الموعد is correct and understandable, but in everyday Egyptian Arabic, many speakers more often say الميعاد for appointment.

So in real-life Egyptian speech, you might very often hear:

• الميعاد يوم الاتنين

But الموعد يوم الاتنين is still clear and correct, especially if the learner is seeing a slightly more formal or neutral wording.

You can keep the same structure and just replace the weekday:

• الموعد يوم التلات = The appointment is on Tuesday
• الموعد يوم الأربع = The appointment is on Wednesday
• الموعد يوم الخميس = The appointment is on Thursday
• الموعد يوم الجمعة = The appointment is on Friday
• الموعد يوم السبت = The appointment is on Saturday
• الموعد يوم الحد = The appointment is on Sunday

So the pattern is:

• الموعد يوم + weekday

This is a very useful everyday template in Egyptian Arabic.