cornerstone

noun
1
a stone at the corner of the base of a building, often laid in a special ceremony
سنگ بنا, سنگ زاویه, سنگِ پایه, سنگِ زاویه
2
the most important part of something that the rest depends on
سنگ بنا, شالوده, زیربنا, اساس
This study is the cornerstone of the whole research programme.