Learn Arabic (Modern Standard): الكلب في حديقتنا.

We use the attached ending ـنا at the very end of the word for garden. In Arabic, possessive pronouns for plural owners like "our" attach directly to the noun instead of being separate words.

Why is there a regular letter "t" (ت) in the middle of حديقتنا?

The basic word for garden is حديقة, which ends with the special letter taa marbuutah (ة). Whenever you attach a possessive ending like ـنا to a word ending in ة, it opens up into a regular ت. This makes it possible to connect the letters smoothly in writing.

Why doesn't the word حديقتنا have the prefix الـ for "the"?

Adding a possessive ending like ـنا already makes the noun definite (specific), meaning it is clearly "our garden" and not just any garden. In Arabic, you cannot put the definite article الـ on a word that also has a possessive ending attached to it.

Where is the word for "is" in this sentence?

There is no word for "is" in the Arabic sentence. For present tense sentences that describe where something is, Arabic simply places the subject (الكلب) right before the location phrase (في حديقتنا) without using a verb for "to be".