underlie

• underly

From Middle English underlien, underliggen, from Old English underliċġan (“to underlie, to be subject to, give way to”), equivalent to under- +‎ lie. Cognate with Dutch onderliggen (“to lie below, lie on the bottom of”), German unterliegen (“to lie under, be subject to, succumb”).

• IPA^(key): /ˌʌn.də(ɹ)ˈlaɪ/
• Rhymes: -aɪ

underlie (third-person singular simple present underlies, present participle underlying, simple 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.

   • 2013 July-August, Sarah Glaz, “Ode to Prime Numbers”, in American Scientist, volume 101, number 4:

     Some poems, echoing the purpose of early poetic treatises on scientific principles, attempt to elucidate the mathematical concepts that underlie prime numbers. Others play with primes’ cultural associations. Still others derive their structure from mathematical patterns involving primes.

4. (transitive) To be subject to; be liable to answer, as a charge or challenge.
   • Sir Walter Scott

     The knight of Ivanhoe […] underlies the challenge of Brian der Bois Guilbert.

5. (mining) To underlay.