Definition of supplemental in US English:

supplemental

adjective

North American
  • Provided in addition to what is already present or available to complete or enhance it.

    ‘many premature infants need supplemental oxygen soon after birth’
    • ‘I plan to use it as a supplemental text for each of the courses I teach.’
    • ‘During years of normal rainfall, supplemental irrigation appears to offer no advantages from the standpoint of yield or quality.’
    • ‘Hyperlinks also were included to point users to supplemental information available on the Internet.’
    • ‘Many student farms are organized as student clubs, making them eligible for supplemental funding from student councils.’
    • ‘A supplemental source of iron must be administered within a few days of birth to prevent anemia.’

Pronunciation

supplemental

/ˌsəpləˈmen(t)l//ˌsəpləˈmɛn(t)l/