underlay

Multiple Entries:
  underlay    underlie  

Concise Oxford English Dictionary © 2008 Oxford University Press:
underlay1

▶verb (past and past part. underlaid) place something under (something else), especially to support or raise it. ▶noun

• 1 material laid under a carpet for protection or support.

• 2 Music the manner in which the words are fitted to the notes of a piece of vocal music.

Concise Oxford English Dictionary © 2008 Oxford University Press:
underlay2

past tense of underlie.

Concise Oxford English Dictionary © 2008 Oxford University Press:
underlie/ʌndəˈlʌɪ/

▶verb (underlies, underlying; past underlay; past part. underlain)

• 1 lie or be situated under.

• 2 (often as adj. underlying) be the cause or basis of.