一昨日（おととい、otoとi）
- the day before yesterday

The Japanese word 一昨日一昨日 means "the day before yesterday." It refers to the day preceding yesterday. It is a time marker used to indicate a point in the past.

⚫︎一昨日、映画を見ました。 Translation: I watched a movie the day before yesterday. ⚫︎一昨日、友達と会いました。 Translation: I met my friend the day before yesterday. ⚫︎一昨日はとても暑かったです。 Translation: The day before yesterday was very hot.

一昨日一昨日 is used in conversations and written Japanese to refer to a specific day in the past. It's used in the same way we use "the day before yesterday" in English. You can use it when talking about events, experiences, or anything that occurred two days prior to the current day.

⚫︎The word is written as 一昨日一昨日. ⚫︎The kanji is used with the reading おととい. ⚫︎一 means "one," 昨日 means "yesterday," ⚫︎There are no other common ways to write this word. The okurigana is fixed.

There are no direct synonyms, as it is a specific time reference.

⚫︎明日（あした） - Tomorrow ⚫︎今日（きょう） - Today ⚫︎昨日（きのう） - Yesterday

一昨日は雨が降って、寒かった。 ・Translation: It rained and was cold the day before yesterday. ・Explanation: This sentence describes the weather conditions on the day before yesterday.

一昨日から熱が出て、まだ治らない。 ・Translation: I've had a fever since the day before yesterday, and it still hasn't gone away. ・Explanation: This sentence explains that the speaker has been sick since the day before yesterday.

The word 一昨日一昨日 is a combination of the kanji 一 (ichi) meaning "one" and 昨日 (kinou) meaning "yesterday". Therefore, it literally means "one yesterday," referring to the day before yesterday.