Learn Hardcore Japanese: zangyou ga ooi hi ha tukaremasu. - On days with a lot of overtime, I get tired.

残業が多い = “(the amount of) overtime is a lot”
残業を多い ❌ (を is for direct objects of verbs, not for this kind of adjective)
残業は多い is possible, but then 残業 becomes the topic (“as for overtime, it is a lot”), which slightly changes the focus and is less natural in this specific pattern before 日.

Here, we’re making a relative clause 残業が多い that modifies 日: “a day when overtime is a lot” → “a day with a lot of overtime.”
Using が is the standard pattern for such clauses with 多い.

How does 残業が多い日 work grammatically? Why is the adjective in front of 日?

残業が多い日 is a relative clause:

残業が多い = “overtime is a lot”
日 = “day”

In Japanese, a whole clause can come directly before a noun and modify it:

残業が多い日
= (a) day when overtime is a lot
≈ “a day with a lot of overtime”

So the pattern is:

[clause] + noun

Examples:

雨が降る日 = “a day when it rains”
仕事が忙しい日 = “a day when work is busy”

Same pattern here:

残業が多い日 = “a day when there is a lot of overtime”

Why is は attached to 日 (日は) to mean “on days …”? Why not use に like 日に?

は here is the topic marker, not a time marker.

The structure is:

残業が多い日 = “days with a lot of overtime”
残業が多い日 は … = “As for days with a lot of overtime, …”

So the sentence is:

残業が多い日は疲れます。
“As for days when I have a lot of overtime, (I) get tired.”

You could say:

残業が多い日には疲れます。

Here に marks the time (“on such days”), and は still marks the topic. But in many cases, Japanese just uses X は and lets context imply “on X” when X is a time word (今日, 週末, 仕事が忙しい日, etc.). So:

週末はゆっくりします。
“On weekends, I relax.”

Same idea as 残業が多い日は疲れます。

Who is the subject of 疲れます? There is no “I” or “we” in the sentence.

Japanese often omits the subject when it’s clear from context.

In this sentence:

残業が多い日 = “days with a lot of overtime”
疲れます = “(someone) gets tired”

In normal conversation, if you’re talking about your own work and your own overtime, it will be naturally understood as:

“On days with a lot of overtime, I get tired.”

To include the subject explicitly, you could say:

私は残業が多い日は疲れます。
私 (I) is just usually dropped when it’s obvious.

Why is the verb 疲れます (polite non-past form) used instead of 疲れました or 疲れています?

疲れます (polite non-past) is used for:

general, habitual statements
“On days with a lot of overtime, I (tend to) get tired.”

If we changed it:

疲れました (past)
- 残業が多い日は疲れました。
  → “On days with a lot of overtime, I got tired.”
  Sounds like you’re reporting about some past period, not a general truth.
疲れています (progressive / state: “am tired”)
- 残業が多い日は疲れています。
  → “On days with a lot of overtime, I’m (in a state of) tired.”
  Grammatically possible, but feels more like describing your current continuous state or talking about specific situations, not a broad rule.

For a general pattern/habit, Japanese typically uses the non-past form:

〜日は疲れます。
〜と、疲れます。

Could I say 残業が多いと疲れます or 残業が多いときは疲れます instead? What’s the difference?

Yes, both are natural, with slightly different nuances:

残業が多いと疲れます。
- と = “when / whenever / if” (cause–effect feel)
- “When there is a lot of overtime, I get tired.”
  General rule, more direct condition → result.
残業が多いときは疲れます。
- とき = “time(s) / when”
- “At times when there is a lot of overtime, I get tired.”
  Focuses on those occasions.
Original: 残業が多い日は疲れます。
- Literally “On days with a lot of overtime, I get tired.”
  Emphasizes the whole day as a unit.

All three are correct and very close in meaning. The original just frames it in terms of “days” rather than “whenever” or “times when.”

Why is the ending 疲れます (polite) and not 疲れる (plain)? What changes if I use 疲れる?

疲れます is the polite form (ます-form).
疲れる is the plain / dictionary form.

Meaning-wise, they are the same (“get tired”), but politeness level changes:

残業が多い日は疲れます。
→ Polite; used with people you’re not close to, at work, etc.
残業が多い日は疲れる。
→ Casual; used with friends, family, or in your own notes.

Japanese changes politeness mostly with the verb ending, not with pronouns like “I/you.”

Could I say 残業の多い日 instead of 残業が多い日? What’s the difference between 〜が多い and 〜の多い?

Both can appear in front of 日, but the nuance is different:

残業が多い日
- Full clause: “days when overtime is a lot”
- Uses が to make a normal sentence-like clause.
- Very natural and common here.
残業の多い日
- More like “days of much overtime / days with much overtime”
- の makes it feel a bit more noun-like / descriptive, sometimes slightly more formal or written, depending on context.

In many everyday cases, 残業が多い日 is more straightforward and natural.
残業の多い日 is not wrong and is used, but learners are usually better off mastering the 〜が多い pattern first.

Does 日 here mean “day” (singular) or “days” (plural)? How can I tell?

Japanese nouns like 日 don’t usually mark singular/plural explicitly. They’re number-neutral.

So 残業が多い日 can be understood as:

“a day with a lot of overtime”
“days with a lot of overtime”

Context tells you whether you’re talking about one day or such days in general. Because the sentence is in a general, habitual form (疲れます), it’s naturally interpreted as:

“On days when I have a lot of overtime, I get tired.” (plural/generic)

Why isn’t there an English-style “on” (like “on days”) in the Japanese sentence?

The function of “on” in English is partly handled by word order and partly by particles in Japanese.

In our sentence:

残業が多い日 = “days with a lot of overtime”
残業が多い日 は … = “As for days with a lot of overtime, …”

This topic structure often naturally translates to “on [those days]” in English. Japanese does not need a separate “on” word; the time expression + は (or sometimes + に/には) already carries that meaning in context.

Compare:

雨の日は家にいます。
Literally: “As for rainy days, I stay at home.”
Natural English: “On rainy days, I stay at home.”

Same pattern as 残業が多い日は疲れます。

How are the words in 残業が多い日は疲れます。 pronounced?

Pronunciation (with typical pitch accent not marked here):

残業 – ざんぎょう (zangyou)
が – ga
多い – おおい (ooi)
日 – ひ (hi)
は – wa (as a particle, it is written は but pronounced “wa”)
疲れます – つかれます (tsukaremasu)

So the whole sentence is:

ざんぎょうがおおいひはつかれます。