underlying

adj

1. (not-comparable)lying underneath

   “We dug down to the underlying rock.”

   “Old Yew, which graspest at the stones ⁠That name the under-lying dead, ⁠Thy fibres net the dreamless head, Thy roots are wrapt about the bones.”

   “During the track renewals, advantage was taken to redrain the area and the old spent ballast was removed down to the underlying rock, new ballast and drains being provided throughout.”

   “Sometimes, the underlying layers are exposed by erosion, revealing the story of the rocks like an open book.”

2. (not-comparable)basic or fundamental

   “Points and straight lines are underlying elements of geometry.”

   “Finding a successful treatment for Alzheimer’s faces two major hurdles: the first being we still don’t know enough about the disease’s underlying biology.”

   “The underlying problem with transport policy is that there no coherent strategy. Ministers have tended to encourage greater use of motor vehicles through both transport and (particularly) planning policies, while simultaneously warning of the terrible consequences of unfettered growth of road use.”

3. (not-comparable)implicit

   “Many nursery rhymes have an underlying meaning.”

noun

1. The entity from whose performance a derivative derives its value.

verb

1. (form-of, gerund, participle, present)present participle and gerund of underlie