Learn Hardcore Japanese: watasi no ie ni neko ga iru.

The particle の marks possession or a genitive relationship. Here, 私の家 literally means my house, linking 私 (I/me) with 家 (house) to show ownership.

Why is に used after 家 instead of another particle like で?

In existence (there is/are) sentences, に indicates the location where something exists. 私の家に means “at my house.” By contrast, で would mark the location of an action, not simple existence.

Why is が used after 猫? Could we use は instead?

が marks the subject in existential sentences, introducing something as existing or present. Using は would make 猫 the topic and imply contrast or known context.

猫がいる: “There is a cat” (introducing its existence).
猫はいる: “As for cats, they do exist” (contrastive/general statement).

Why is the verb いる used instead of ある?

Japanese distinguishes animate vs. inanimate existence.

いる is used for living beings (people, animals).
ある is used for inanimate objects or abstract things.
Since a cat is animate, you must use いる.

Why isn’t there a verb meaning “have” in this sentence?

Instead of a direct equivalent of “have,” Japanese often expresses possession by stating that something exists at a location.
私の家に猫がいる literally means “At my house, a cat exists,” which naturally corresponds to “I have a cat.”

Could the word order be changed? For example, 猫が私の家にいる?

Yes. Japanese word order is flexible because particles mark grammatical roles.

私の家に猫がいる focuses first on the location.
猫が私の家にいる brings the cat (subject) to the front.
Both are grammatical; they just shift the emphasis.

Is it necessary to include 私の? Could I just say 家に猫がいる?

You can omit 私の if the context makes it clear whose house you mean.

家に猫がいる means “There’s a cat at (my/your/our) house,” depending on context.
Including 私の removes any ambiguity and specifies my house.

What’s the difference between いる and its polite form います?

いる is the plain/dictionary form, used in casual speech or writing.
います is the polite form, used when speaking formally or respectfully.
Both mean “to exist” for animate subjects; you choose based on the level of politeness you need.