Reminiscence
Noun, する verb, and の adjective
かいそう
この映画のこの回想のシーンがすごくすきなんだよね。
I really like this retrospective scene in the movie.
コウイチはえんがわでネコと一しょにとりとめのない回想にふけっていた。
Koichi was reminiscing incoherently with his cat on the veranda.
ビエトが時々、仕事中にヤクザ時代のことを回想しているのをわたしは知っている。
I know that Viet sometimes reminisces about his yakuza days during work hours.
You think about the concept of a certain number of times, each time thinking of each time you've thought about this concept before. Each time you look back, that is retrospection on that concept. You look back more and more times until there are no more times to look back on.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.