Definitions:

1. education or instruction in the fundamentals of a field of knowledge noun
   • They lack the foundation necessary for advanced study.
2. the basis on which something is grounded noun
   • There is little foundation for these objections.

Synonyms:

• base
• basis
• cornerstone
• foot
• foundation garment
• fundament
• grounding
• groundwork
• initiation
• substructure
• understructure