Denshi Jisho — Online Japanese dictionary

系 けい 1: system; lineage; group;
2: (Mathematical term) corollary;
3: (geological) system (range of strata that correspond to a particular time period);
4: (taxonomical) series
Common word, Noun, Noun suffix 
家系 かけい family lineage
Common word, Noun 
系図 けいず family tree; pedigree; genealogy
Common word, Noun 
系譜 けいふ genealogy; pedigree
Common word, Noun 
理系 りけい science
Common word, Noun, No-adjective 
河系 かけい river system
Noun 
区系 くけい ecozone (biogeographical realm)
Noun 
父系 ふけい agnate
Noun, No-adjective 
母系 ぼけい maternal line; mother's side of the family
Noun, No-adjective 
系統 けいとう system; family line; geological formation; lineage; ancestry
Common word, Noun 
系列 けいれつ 1: series; sequence; system; order of succession;
2: keiretsu (conglomeration of businesses linked by cross-shareholdings)
Common word, Noun 
山系 さんけい mountain range; mountain system
Common word, Noun 
水系 すいけい drainage system
Common word, Noun 
体系 たいけい system; organization; organisation; architecture
Common word, Noun 
日系 にっけい (of) Japanese descent
Common word, Noun, No-adjective 
文系 ぶんけい humanities, social sciences, and fine arts; liberal arts
Common word, Noun, No-adjective 
一系 いっけい single-family lineage
Noun 
Ａ系 エーけい Akihabara style; nerdy
Noun, No-adjective, Abbreviation, Slang 
国系 こっけい country of origin; ethnicity
Suffix 
女系 じょけい female line; matrilinear
Noun 
正系 せいけい legitimate line; direct descent
Noun 
大系 たいけい outline; survey; compendium
Noun 
男系 だんけい male lineage
Noun, No-adjective 
同系 どうけい affiliated; akin
Noun, No-adjective 
女系 にょけい female line; matrilinear
Noun 
Ｂ系 ビーけい hip-hop culture; Black culture (esp. breakdancing culture)
Noun, No-adjective, Slang 

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