N3
っけ
What is…again?, Was it... that... ?, Did you say...?
今日の朝は朝ご飯を食べたっけ。
Did I eat breakfast this morning?
Explanation
「っけ」 has 2 uses
1Checking what you forgot
You can't remember and check with someone or yourself: 「今日は何曜日だっけ?」
そんなもの家にあったっけ?
Did we have something like that at home?
今日の朝は朝ご飯を食べたっけ。
Did I eat breakfast this morning?
2Fondly recalling
Talking to yourself about the past, often 「〜たっけ」: 「子供の頃、よくこの川で遊んだっけ」 (I used to play by this river as a kid).
学生の頃は、毎晩友達と電話したっけなあ。
Back in school, I used to call friends every night.
昔はこの駅の前に、小さな本屋があったっけ。
There used to be a little bookshop in front of this station.
Mixed up with
Only for something you once knew and have momentarily forgotten. It can't be used for something you never knew: meeting someone for the first time, you can't ask 「あなたのお名前は何だっけ?」; say 「お名前は何とおっしゃいますか」.
The polite forms are 「〜でしたっけ」 and 「〜ましたっけ」, natural for checking small things with coworkers.