un ‧ der ‧ lie AC /ˌʌndəˈlaɪ $ -ər-/ BrE AmE verb ( past tense underlay /-ˈleɪ/, past participle underlain /-ˈleɪn/, present participle underlying , third person singular underlies ) [transitive] formal
[ Word Family: verb : ↑ underlie ; adjective : ↑ underlying ]
to be the cause of something, or be the basic thing from which something develops:
the one basic principle that underlies all of the party’s policies
⇨ ↑ underlying