Definitions:

1. At the beginning. adverb
   • The research was conducted ab initio, starting from first principles.
2. From the start; from scratch. ADJECTIVE
   • The project was doomed to fail ab initio due to insufficient planning.
3. In legal contexts, it often refers to actions or agreements that are considered void from the beginning, indicating that they are treated as if they never existed. ADJECTIVE
   • An invalid or cancelled contract is not legally binding ab initio.

Synonyms:

• initially
• Originally
• Primarily
• To begin with