первопричи́на первопричина

Meanings

1. first cause, prime cause, root cause, primary cause, ultimate cause
2. initial cause
3. original cause

Examples

• Эгои́зм — э́то первопричи́на ра́ка души.
  Egoism is the prime cause of cancer of soul.
• У всякого следствия есть своя первопричина.
  Every effect has its first cause.