الكرة في الحديقة.

In present-tense Arabic, a sentence like this usually does not need a word for is.
So الكرة في الحديقة literally looks like the ball in the garden, but it naturally means The ball is in the garden.

Arabic does use words like كان for was or related meanings in other tenses, but not normally for a simple present-tense statement like this.

It is a nominal sentence (جملة اسمية), because it begins with a noun rather than a verb.

In traditional grammar:

• الكرةُ is the subject/topic (مبتدأ)
• في الحديقةِ is the predicate/comment (خبر)

So the structure is basically:

• the ball
  • in the garden

Because الـ is the Arabic definite article, equivalent to the.

So:

• الكرة = the ball
• الحديقة = the garden

Arabic puts الـ directly onto the noun, instead of using a separate word like English the.

في means in. It is a preposition.

In Arabic, prepositions make the following noun genitive. So in a fully vowelled version, you would read:

• في الحديقةِ

The final -i sound on الحديقةِ shows that it is after a preposition.

With full vowel marks, it is:

الْكُرَةُ فِي الْحَدِيقَةِ

A careful MSA pronunciation is:

al-kuratu fī al-ḥadīqati

In normal pause, many speakers drop the final case vowels, so it often sounds more like:

al-kurah fī al-ḥadīqah

Because ك in الكرة and ح in الحديقة are moon letters.

With moon letters, the l of الـ is pronounced clearly:

• al-kurah
• al-ḥadīqah

If the next letter were a sun letter, the l would assimilate and not be pronounced separately.

That letter is called taa marbuta (ة).

It often marks a noun as grammatically feminine. In pause, it is usually pronounced like -a or -ah:

• الكرة → al-kurah
• الحديقة → al-ḥadīqah

But when grammatical endings are pronounced, it acts like t:

• الْكُرَةُ
• الْحَدِيقَةِ

Because they have different grammatical roles.

• الكرةُ is the subject/topic of the nominal sentence, so it is nominative
• الحديقةِ comes after the preposition في, so it is genitive

So the endings reflect grammar, not meaning alone.

In most everyday Arabic writing, these short vowel endings are not written.

Yes, both are grammatically feminine. The ة at the end is a strong clue.

This matters when other words agree with them. For example:

• الكرة كبيرة = The ball is big

Here كبيرة is the feminine form of big.

Yes, but الكرة في الحديقة is the most neutral way to say it.

You can sometimes move the prepositional phrase first:

• في الحديقةِ الكرةُ

But that sounds more marked or literary, and it changes the emphasis. Arabic word order is often flexible, but different orders can sound more or less natural depending on context.

You could say:

كُرَةٌ في الحديقةِ

Here كُرَةٌ is indefinite, so it means a ball rather than the ball.

This can also feel similar to English There is a ball in the garden, depending on context.

You can say:

الكرة ليست في الحديقة

This means The ball is not in the garden.

ليست is used here to negate the nominal sentence, and it is feminine singular to match الكرة.