what is ”Koseki=戸籍”？　

It is a public book that describes the relationship between a married couple and their family (a book kept by government offices in accordance with laws and regulations) and is under the control of the municipalities.

夫婦とその家族の身分関係を記した公簿（官公署が法令に基づき常置く帳簿）であり、市町村の管掌下にあります。

●戸籍謄本（Kosekitouhon)=copy of family register 

A copy of the entire family register

戸籍の全部を写し取ったもの。

●戸籍抄本(Kosekishouhon)=partial copy of family register

A copy of a specific person's part from the family register

戸籍の中から特定の人の部分だけを写し取ったもの。

●本籍（Honseki)=permanent domicile　

A government office that stores family registers. Also called "Seki".

戸籍を保管している役所役場。「籍」とも言う。

●戸籍法(Kosekihou)=Family register law 

Family register law to clarify the relationship between individuals

各個人の身分関係を明らかにする為の戸籍の法律。

●戸主 (Koshu)=Householder 

●除籍(Jyoseki)=To leave the family register

Also referred to as "Seki wo nuku"

戸籍から名前を抜く事、「籍を抜く」とも言う。