هذا الكتاب متاح.

A natural word-by-word breakdown is:

• هذا = this
• الكتاب = the book
• متاح = available

So the whole sentence means This book is available.

A useful learner shortcut is:

• هذا الكتاب = this book
• متاح = available

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

So:

• هذا الكتاب متاح literally looks like this book available
• but it means This book is available

This is very normal in Arabic. In the present tense, Arabic often just places the subject next to the description.

If you wanted a past or future meaning, Arabic would use other words, for example:

• كان هذا الكتاب متاحًا = This book was available
• سيكون هذا الكتاب متاحًا = This book will be available

هذا is the masculine singular demonstrative, meaning this.

It is used because كتاب (book) is:

• singular
• masculine

So the demonstrative has to match.

Compare:

• هذا الكتاب = this book
• هذه المجلة = this magazine (feminine)

So the choice of هذا tells you the noun is masculine singular.

In Modern Standard Arabic, the demonstrative normally comes before the noun:

• هذا الكتاب = this book

This is the standard order in MSA.

So you should learn the pattern:

• هذا + noun for masculine singular
• هذه + noun for feminine singular

Even though adjectives usually come after the noun in Arabic, demonstratives like هذا come before it.

This is a very common question.

In Arabic, after a demonstrative like هذا, the noun is usually definite, and in MSA it commonly appears with الـ:

• هذا الكتاب literally: this the-book

That sounds strange in English, but it is normal Arabic.

So when you translate, you do not say this the book. You simply say:

• this book

This is just a structural difference between Arabic and English.

Yes, in this sentence متاح functions like an adjective meaning available.

It agrees with the noun it describes:

• الكتاب is masculine singular
• so متاح is also masculine singular

If the noun were feminine singular, you would usually use:

• متاحة

For example:

• هذه الغرفة متاحة = This room is available

So متاح changes according to gender and number, just like many Arabic adjectives.

If the sentence were fully vowelled in careful formal Arabic, it would usually be:

• هٰذَا الْكِتَابُ مُتَاحٌ

The endings are:

• هٰذَا — this word is fixed here
• الْكِتَابُ — nominative
• مُتَاحٌ — nominative

Why nominative? Because this is a nominal sentence in which:

• هذا الكتاب is the topic/subject part
• متاح is the predicate

In everyday printed Arabic, these short vowels are usually omitted, so you normally just see:

• هذا الكتاب متاح

A careful MSA-style pronunciation is approximately:

• hādhā al-kitābu mutāḥ(un)

A few pronunciation notes:

• ذ in هذا sounds like the th in this
• كِتاب has stress roughly on -tāb
• ح in متاح is a stronger, breathier sound than English h

In normal pause at the end of the sentence, the final case ending is often not pronounced, so you may hear something closer to:

• hādhā al-kitāb mutāḥ

Because متاح is the masculine singular form.

Arabic adjectives often have a basic masculine form and a feminine form made with ـة:

• متاح = masculine singular
• متاحة = feminine singular

Since الكتاب is masculine, the sentence uses:

• متاح

If the noun were feminine, you would say:

• هذه الفرصة متاحة = This opportunity is available

Yes. This is a very useful pattern:

• هذا + noun + adjective

Examples:

• هذا القلم جديد = This pen is new
• هذا الفندق مفتوح = This hotel is open
• هذا المقعد محجوز = This seat is reserved

And for feminine nouns:

• هذه السيارة جديدة = This car is new

So هذا الكتاب متاح is a good model sentence to reuse.

For a beginner, the easiest way to understand it is:

• هذا الكتاب = this book
• متاح = available

So the whole sentence is:

• [this book] [available]

In more advanced grammar, هذا can be analyzed as the main demonstrative element, with الكتاب attached to it in apposition/explanation. But you do not need that analysis to understand or use the sentence correctly.

For practical learning, it is best to treat هذا الكتاب as one phrase meaning this book.