underlie

To be the real cause, basis, or foundation of something, often not immediately obvious.

• underlying/ˌʌndəˈlaɪɪŋ/(adj)根本的/潜在的

• underlying cause
• underlying issue
• underlying assumption
• underlying principle

1. 1.Economic inequality underlies many social problems. (root cause)
2. 2.The underlying assumption is that demand will keep growing. (hidden basis)

• underpin/ˌʌndəˈpɪn/— provide structural support
• form the basis of (explain clearly)
• be at the root of (informal)

under + lie — to lie beneath the surface