هذه بداية الدرس.

A careful MSA pronunciation is:

hādhihi bidāyatu d-darsi

If you pause at the end, it is often pronounced more like:

hādhihi bidāyat ad-dars

A few notes:

• هذه = hādhihi
• بداية = bidāya when said alone, but here it becomes bidāyatu / bidāyat because of the grammar
• الدرس = ad-darsi / ad-dars, not al-dars, because د is a sun letter, so the l sound of ال assimilates

Because بداية is a feminine noun.

In Arabic, demonstratives must agree with the noun in gender:

• هذا = this for masculine nouns
• هذه = this for feminine nouns

Since بداية is feminine, Arabic says:

• هذه بداية...

not:

• هذا بداية...

Because it ends in ة (tāʾ marbūṭa), which is one of the most common signs of a feminine noun in Arabic.

So:

• بداية = beginning
• It is grammatically feminine
• Therefore it takes هذه

This is grammatical gender, not biological gender. English learners often need to get used to the fact that words like beginning, city, or car can be grammatically masculine or feminine in Arabic.

In present-tense Arabic, the verb to be is usually not stated in sentences like this.

So:

• هذه بداية الدرس literally looks like this beginning the-lesson
• but it means This is the beginning of the lesson

This is very normal in Arabic nominal sentences.

If you wanted to talk about the past, you would use a verb such as كان:

• كانت هذه بداية الدرس = This was the beginning of the lesson

This is an iḍāfa construction, often called a construct phrase.

It means:

• بداية = beginning
• الدرس = the lesson
• بداية الدرس = the beginning of the lesson

In an iḍāfa:

1. the first noun is the thing possessed or defined
2. the second noun tells what it belongs to or is connected to

So here:

• بداية = the beginning
• الدرس = of the lesson

Because in an iḍāfa, the first noun usually does not take ال when it is being defined by the second noun.

Compare:

• بداية = a beginning
• بداية الدرس = the beginning of the lesson

Even though بداية has no الـ, the whole phrase becomes definite because الدرس is definite.

So بداية الدرس is already definite and means the beginning of the lesson, not just a beginning of a lesson.

Because in an iḍāfa construction, the second noun is put in the genitive case.

So in full vowelled Arabic:

• بدايةُ = nominative
• الدرسِ = genitive

That is why you may see:

هذه بدايةُ الدرسِ

The genitive ending on الدرس is part of the grammar of iḍāfa.

Because بداية is followed by another noun in an iḍāfa construction.

The final ة (tāʾ marbūṭa) is often pronounced:

• like -a / -ah when the word stands alone or at pause
• like -t when the grammar connects it to what follows

So:

• alone: bidāya
• in this sentence: bidāyat(u) d-darsi

This is very common in Arabic and important for listening and reading.

Because د is a sun letter.

When الـ comes before a sun letter, the l sound is not pronounced. Instead, the following consonant is doubled.

So:

• written: الدرس
• pronounced: ad-dars

Other examples:

• الشمس → ash-shams
• الطالب → aṭ-ṭālib
• النور → an-nūr

The spelling stays the same, but the pronunciation changes.

A simple analysis is:

• هذه = demonstrative pronoun, this
• بدايةُ الدرسِ = predicate, the beginning of the lesson

So the sentence is a nominal sentence:

• هذه = the topic
• بداية الدرس = what is being said about it

In traditional grammar terms:

• هذه = mubtadaʾ
• بدايةُ = khabar
• الدرسِ = muḍāf ilayhi

Yes, but هذه بداية الدرس is the most straightforward and natural way to say it in MSA.

Arabic does allow some flexibility, but changing the order may make the sentence sound more formal, marked, or less natural for a beginner pattern.

So for learners, it is best to remember:

• هذه بداية الدرس

as the normal model.

In fully vocalized formal Arabic, the sentence is:

هٰذِهِ بِدايةُ الدَّرْسِ

More explicitly in transliteration:

hādhihi bidāyatu d-darsi

The endings are:

• بدايةُ = -u because it is nominative
• الدرسِ = -i because it is genitive in the iḍāfa

In normal printed Arabic, these short vowels are usually omitted, so learners often just see:

هذه بداية الدرس

Yes. بداية can often be translated as:

• beginning
• start

So depending on context, the sentence could be rendered naturally in English as:

• This is the beginning of the lesson
• This is the start of the lesson

The Arabic meaning stays the same; the English wording can vary a little.