• IPA: /ˌʌn.də(ɹ)ˈlaɪ/

underlie (underlies, present participle underlying; past underlay, past participle underlain)

1. (intransitive) To lie in a position directly beneath.
2. (transitive) To lie under or beneath.

   A stratum of clay underlies the surface gravel.

3. (transitive) To serve as a basis of; form the foundation of.

   a doctrine underlying a theory

   • 1941, Emily Carr, Klee Wyck, Chapter 6,

     […] she was carved into the bole of a red cedar tree. Sun and storm had bleached the wood, moss here and there softened the crudeness of the modelling; sincerity underlay every stroke.

4. (transitive) To be subject to; be liable to answer, as a charge or challenge.
   • 1820, Walter Scott, Ivanhoe; a Romance. [...] In Three Volumes, volume (please specify ), Edinburgh: Printed for Archibald Constable and Co.; London: Hurst, Robinson, and Co. […], OCLC 230694662 ↗:

5. (mining) To underlay.

• German: zugrunde liegen
• Spanish: subyacer