1Pretty, lovely, or beautiful in appearance — used broadly for people, scenery, flowers, clothing, anything visually pleasing. A fundamental everyday word. Because 綺 is non-jōyō, modern writing tends to use the kana spelling きれい, but the kanji form 綺麗 remains common in beauty/fashion/lifestyle media, lyrics, and literary prose where its visual impression carries weight.
桜が満開で、本当にきれいだった。
The cherry blossoms were in full bloom — truly beautiful.
彼女は今日、いつもより綺麗に見える。
She looks prettier than usual today.
このドレス、すごくきれいな色ですね。
What a lovely color this dress has.
ホテルの窓から見える夜景がきれいで、思わず写真を撮った。
The night view from the hotel window was so beautiful that I couldn't help taking a photo.
おばあちゃんは年を取っても字がとてもきれいだ。
Even now that she's older, my grandmother still has very beautiful handwriting.
2Clean, tidy, or pure — free of dirt, clutter, or contamination. Used for rooms, water, air, the body, etc. In this sense, the kana spelling きれい is particularly common.
部屋をきれいに片付けてから出かけた。
I tidied up the room before going out.
ご飯の前は手をきれいに洗ってね。
Wash your hands properly before meals.
この川は水がきれいで、魚が泳いでいるのが見える。
The water in this river is so clear you can see the fish swimming.
彼のデスクはいつもきれいに整っている。
His desk is always neatly organized.
3Used adverbially as 'きれいに' to mean 'completely, entirely, without a trace.' Expressions like きれいに忘れる (forget completely), きれいに食べる (finish off entirely), or きれいに消える (vanish without a trace). This sense departs from the literal meaning of the kanji and is normally written in kana.
子どもがお弁当をきれいに食べきった。
The child polished off the entire bento without leaving a scrap.
雪は朝までにきれいに溶けてなくなっていた。
By morning the snow had melted away completely.
昔の彼氏のことはきれいに忘れた。
I've completely forgotten about my ex.
ローンをきれいに返し終えて、ようやくほっとした。
I finally felt relieved after paying off the loan in full.