Learn Hardcore Japanese: kono heya no tenzyou ha takai desu.

その means “that” (near the listener): その部屋 = “that room (near you)”.
あの means “that” (away from both speaker and listener): あの部屋 = “that room over there.”

What does the particle の do in 部屋の天井?

The particle の marks a possessive or descriptive relationship, similar to “of” in English.

部屋の天井 literally means “ceiling of the room.”
It links 部屋 (room) to 天井 (ceiling).

Why is は used after 天井 instead of が?

は is the topic marker, showing that “the room’s ceiling” is what we’re talking about. It often implies known or general information.
が is the subject marker, emphasizing new or specific information.
Here, we’re making a general statement about the ceiling, so we use は.

Why is 高い placed before です?

In Japanese, i-adjectives like 高い can directly function as predicates. To make the sentence polite, you simply add です after the adjective:

Casual: 高い (“is high”)
Polite: 高いです (“is high” + polite copula)

Can we omit です and just say この部屋の天井は高い?

Yes. In casual speech or writing, omitting です is common: この部屋の天井は高い.
In formal or polite contexts, you keep です to maintain the polite tone.

How does the word order in Japanese compare with English?

Japanese typically follows Topic–Object–Verb (or predicate) order, with the verb/adjective clause at the end.

Here: この部屋の天井は (topic) + 高いです (predicate “is high”).
English follows Subject–Verb–Complement: “The ceiling of this room is high.”

How do you pronounce 天井, and what do the Kanji mean?

天井 is pronounced てんじょう (tenjō).

天 means “heaven” or “sky.”
井 means “well.”
Together they historically referred to the “well to the sky,” now meaning “ceiling.”

Could we rephrase using the noun 高さ (“height”) instead of the adjective 高い?

Yes. To focus on “height,” you’d say:
この部屋の天井の高さは高いです。
Here you link 天井 to 高さ with の (“ceiling’s height”), then mark 高さ as the topic with は, and finish with 高いです.