Learn Hardcore Japanese: watasi ha hasi wo wasuremasita.

は (wa) marks the topic: what the sentence is about. Here, 私 (わたし, I) is the topic: “As for me…”
を (o) marks the direct object of the verb. 箸 (はし, chopsticks) is what was forgotten.
So the structure is Topic (私) + Object (箸) + Verb (忘れました).

Why is は pronounced “wa,” and を pronounced “o”?

The topic particle は is historically spelled with は but pronounced “wa.” This is a special rule for the particle only.
The object particle を is pronounced “o” in modern standard Japanese (though it keeps the old spelling を).

Can I drop 私? When would I say it?

Yes. Japanese often omits the subject when it’s clear. 箸を忘れました is perfectly natural.
Use 私 when you need to make the subject explicit (new topic, contrast, emphasis, or to avoid ambiguity).

What’s the difference between 私は箸を忘れました and 私が箸を忘れました?

私は… sets “me” as the topic; it’s neutral and common.
私が… marks “I” as the grammatical subject and often emphasizes “it was I (not someone else) who forgot.”
Use が when you’re correcting or highlighting who did it.

Does the verb have to be at the end? How flexible is the word order?

Japanese is generally SOV (Subject–Object–Verb). The verb goes last.
You can topicalize elements: 箸は忘れました (“As for the chopsticks, I forgot them.”) adds contrast or emphasis on 箸.
You can reorder phrases somewhat, but particles must stay attached to the words they mark. The safest neutral order is topic–object–verb.

What form is 忘れました? How is it different from 忘れた?

Is 忘れる transitive or intransitive?

忘れる is transitive; it takes a direct object with を: 名前を忘れた (“I forgot [a] name”), 鍵を忘れた (“I forgot my keys”).

Does this mean “I forgot to bring my chopsticks” or “I left my chopsticks somewhere”?

箸を忘れました by itself usually implies you don’t have them because you forgot them (either forgot to bring them or left them behind). Context fills in which.
To be explicit:
- Forgot to bring: 箸を持ってくるのを忘れました.
- Left behind somewhere: 箸を置き忘れました (“left behind”) or 箸を忘れてきました (“I forgot them and came here”).

How do I say “I forgot my chopsticks at home”?

Most natural: 家に箸を忘れてきました (I left them at home and came).
Also heard: 家に箸を忘れました (acceptable, though 〜てきました better captures the “left at home and now here” nuance).

Should I say 箸 or お箸?

お箸 adds a polite, soft tone with the honorific prefix お. Very common in everyday polite speech.
箸 is plain and not rude; use it in neutral/casual contexts.
In service situations, prefer お箸: e.g., お箸をください.

Is 箸 singular or plural? How do I say “a pair of chopsticks”?

Japanese nouns don’t mark singular/plural; 箸 can mean “chopstick(s).”
To specify a pair, use the counter 膳 (ぜん):
- One pair: 一膳 (いちぜん) の箸
- Two pairs: 二膳 (にぜん), etc.

How do I make this more casual or show regret?

Casual: 箸忘れた, or drop the particle in speech: 箸、忘れた.
Casual regret: 箸、忘れちゃった (＝忘れてしまった contracted).
Polite regret: 箸を忘れてしまいました (adds an “unfortunately”/completion nuance).
Very formal/business (not for chopsticks usually): 失念しました (I failed to recall).

What should I say in a restaurant or store if I need chopsticks?

What’s the nuance difference among 忘れました, 忘れてしまいました, and 忘れていました?

忘れました: plain “I forgot.”
忘れてしまいました: “I ended up forgetting”/“I unfortunately forgot” (completion + regret).
忘れていました: “I had forgotten (until just now)”—describes a past state discovered later.

Any pronunciation and writing gotchas with this sentence?

Pronunciation:
- 箸 (はし) is a homophone with 橋 (bridge) and 端 (edge) but different in Tokyo pitch accent:
  - 箸: accented on the first mora (háshi, accent 1)
  - 橋: accent on the second (hashí, accent 2)
  - 端: flat (hashi, accent 0)
- Particle は is pronounced “wa”; を is “o.”
Writing:
- It’s fine to write all in kana: わたしははしをわすれました (though normally no spaces).
- Japanese ordinarily doesn’t use spaces; the spacing you saw is for learners.