1Thanks or gratitude — a feeling or expression of appreciation, often used as お礼.
手伝ってもらったので、彼に礼を言った。
Since he helped me, I thanked him.
せめてもの礼として、お菓子を渡した。
I gave some sweets as a small token of thanks.
礼の一つも言わずに立ち去った。
He left without even saying a word of thanks.
2Manners or etiquette — the socially expected, respectful way of behaving.
目上の人には礼を尽くすべきだ。
You should show proper manners toward your superiors.
礼を知らない態度だと思われたくない。
I don't want to be seen as someone with no manners.
武道では礼に始まり礼に終わると言われる。
In martial arts, it's said that everything begins and ends with proper etiquette.
3A bow — the act of bending the body, done as a formal greeting or sign of respect or gratitude.
授業の始めと終わりに礼をする。
We bow at the beginning and end of class.
彼は深々と一礼をして退場した。
He gave a deep bow and left the stage.
神前では二礼二拍手一礼が基本の作法だ。
The basic manner of worship at a shrine is two bows, two claps, and one bow.
4A reward or gift given as a token of thanks or appreciation.
お世話になった先生に礼を渡した。
I gave a gift to the teacher who had helped me.
見つけてくれたら礼をすると約束した。
I promised a reward if they found it for me.
5A ceremony or ritual — a formal or religious procedure carried out according to set customs.
卒業式の礼は厳かに行われた。
The graduation ceremony was conducted solemnly.
古来の礼にのっとって式を進めた。
The ceremony proceeded according to ancient rites.
6Abbreviation for 礼金 (reikin) — non-refundable 'key money' a tenant pays to a landlord when renting.
このアパートは礼一か月、敷金二か月が必要だ。
This apartment requires one month's key money and two months' deposit.