Learn Hardcore Japanese: kumo ga ooi yoru ha, hosi ga zenzen miemasen. - On nights with many clouds, you can't see the stars at all.

The は marks 夜 (night) as the topic: “As for nights when there are many clouds…” It frames the time setting and makes a general statement about such nights. You could also use 夜には to emphasize the time/location a bit more (“on such nights, at night”), but plain 夜は is the most neutral topic marking here.

Why does が appear twice (雲が and 星が)? Isn’t that wrong?

It’s fine. The first が is inside a noun‑modifying clause (雲が多い) that describes 夜 (“a night when there are many clouds”). The second が marks the subject of the main clause (星が全然見えません). Japanese often allows multiple が when one is inside a subordinate/relative clause.

How does 雲が多い modify 夜? Is this like a relative clause?

Yes. 雲が多い is a full clause meaning “there are many clouds,” used attributively to modify 夜: “a night when there are many clouds,” i.e., “a cloudy night.” Japanese freely uses clauses to modify nouns this way.

Why is it 多い and not 多いです before 夜?

Clauses and adjectives that directly modify a noun must be in the plain (dictionary) form. You can’t use です/ます inside a noun modifier. So it’s 雲が多い夜, not ×雲が多いです夜. This is true for all such modifiers.

Do I ever add だ to an い‑adjective like 多い?

No. い‑adjectives (like 多い、広い、寒い) never take だ. The copula だ/です attaches to nouns and な‑adjectives (e.g., 静かだ, きれいだ), not to い‑adjectives.

Could I say 雲の多い夜 instead of 雲が多い夜?

Yes. 雲の多い夜 is also natural. Nuance:

雲が多い夜 sounds like a direct description “nights when there are many clouds” (event/existence feel).
雲の多い夜 treats “cloud-amount” as a property (“cloudy-ness” as an attribute). Both are common; 雲が多い夜 may feel a bit more descriptive and casual.

Why 星が and not 星は or 星を?

星が is the neutral subject marking with 見える (“to be visible”).
星は would add a contrast/topic nuance: “As for the stars, (they’re not visible)”—implying maybe other things are visible.
星を is wrong here because 見える is intransitive; it does not take を. You’d use を with the transitive verb 見る (e.g., 星を見ます “I look at stars”).

Why 見えません and not 見ません?

見えません is “are not visible/cannot be seen” (intransitive, state). 見ません is “do not look (at)” (transitive, volitional action). The sentence describes a visibility condition, so 見えません is the correct verb.

Is 見えません the potential of 見る? Shouldn’t it be 見られません?

見える is a separate intransitive verb meaning “to be visible; can be seen (by nature).” It’s not simply the potential of 見る.

星が見えません = “The stars aren’t visible.”
星が見られません is grammatical but usually odd here because it means “(I) can’t see the stars” (ability/permission nuance) and normally takes a human subject: 私は星が見られません. For natural phenomena, 見える/見えない is preferred.
Note: Colloquial potential of 見る is 見れる, but standard is 見られる.

What does 全然 do here? Does it always go with negatives?

全然 (ぜんぜん) intensifies to “not at all/completely (not)” when paired with a negative: 全然見えません = “(they) aren’t visible at all.”
Colloquially, people also use 全然 with positives (e.g., 全然大丈夫), but in careful writing/classroom Japanese, it’s safest with negatives. A more formal alternative is 全く (まったく).

Where can 全然 go in the sentence?

Common placements:

星が全然見えません (default)
全然星が見えません (puts stronger focus up front)
星は全然見えません (with は adds a contrastive topic) Don’t put it after the verb. It typically precedes what it modifies.

Could I say ほとんど instead of 全然?

Yes, but the meaning changes:

全然見えません = “not visible at all (0%).”
ほとんど見えません = “hardly visible (almost 0%, but maybe a little).” Pick based on how strong you want the statement to be.

Are spaces required between words?

No. The spaces are just for learners. Natural Japanese writes it without spaces: 雲が多い夜は、星が全然見えません。

How do you read each word?

雲: くも (kumo)
多い: おおい (ooi)
夜: よる (yoru)
星: ほし (hoshi)
全然: ぜんぜん (zenzen)
見えません: みえません (miemasen)

Could I use 曇り instead of 雲? What about 曇った?

曇りの夜 = “a cloudy night” (noun “cloudiness” + の).
曇った夜 = “a clouded-over night” (verb 曇る in past attributive, giving a state).
雲が多い夜 focuses on the quantity of clouds (“nights with many clouds”).
All are acceptable; choose based on nuance and style.

Why is there a comma after 夜は?

The comma 、 separates the topic from the comment, improving readability. It’s optional but common, especially when the topic is longer. Without it, it’s still grammatical.

Is 星が全然見えません different from 星は全然見えません?

Yes:

星が全然見えません states the fact neutrally: “The stars aren’t visible at all.”
星は全然見えません uses は to contrast or limit the statement to stars: “As for the stars, (they) aren’t visible at all (though something else might be).”

Can I say 雲は多い夜?

Generally no; 雲は多い夜 is unnatural because は inside a noun‑modifying clause often creates a contrast that clashes with simple description. Use 雲が多い夜 or 雲の多い夜 instead.

How would I make this casual or change the tense?

Casual present: 雲が多い夜は、星が全然見えない。
Past: 雲が多い夜は、星が全然見えませんでした。 (polite) / 見えなかった。 (casual)
Habitual/general statement usually uses non‑past as in the original.