Japanese Descent
Japanese Origin, Japanese-Operated
noun, の adjective
The 日 stands for 日本 here, making it mean "Japanese." So what's a more common way of saying Japanese lineage? That would be Japanese descent or Japanese origin.
日系 can be used for both people and entities, such as 日系アメリカ人 (Japanese-American) or 日系企業 (Japanese-operated company).
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.
ロサンゼルスには多くの日系アメリカ人が住んでいます。
Many Japanese Americans live in Los Angeles.
アメリカで日系企業につとめるメリットは何ですか。
What are the merits of working for a Japanese company in America?
私は日系の飛行機しか乗らないようにしています。
I only use Japanese airlines.
私の妻は日系アメリカ人の三世です。
My wife is a third-generation American of Japanese descent.