The Hebrew noun yachas (יַחַשׂ) refers to genealogy, family record, or enrollment by lineage. It is used almost exclusively in the post-exilic books of Ezra, Nehemiah, and Chronicles, describing the careful documentation of family lines for purposes of tribal identity, priestly qualification, and inheritance.
Yachas reflects the profound biblical concern for lineage and identity. After the exile, knowing one's genealogy determined whether one could serve as a priest, receive tribal allotments of land, or claim membership in the covenant community. Theologically, this word points to the importance of being properly enrolled in God's family — a concept fulfilled in the New Testament where believers are adopted into God's household and their names written in the Lamb's Book of Life (Revelation 21:27).