Definition of youthfulness in US English:

youthfulness

noun

  • 1The fact of being young.

    ‘his relative youthfulness counted against him in business circles’
    • ‘He delights in the youthfulness of his live show crowds.’
    • ‘The average age of participants is about 22.5, so there's no denying their youthfulness.’
    • ‘She delights in flaunting her youthfulness in the face of her older colleagues.’
    • ‘Qualities people attribute to skin - sensuality, youthfulness, vitality, beauty, even goodness - are also qualities they see in themselves.’
    • ‘It shocked me too to see the youthfulness of some of the most intoxicated people.’
    1. 1.1 Behavior or appearance characteristic of young people.
      ‘the eternal youthfulness of Sir Richard was infectious’
      • ‘These phytonutrients which are powerful in their ability to protect the body and the mind from degeneration and maintain youthfulness.’
      • ‘If you plan to live beyond 70, calcium-rich foods such as milk can help protect your youthfulness.’
      • ‘Here is Vasiliev at 60, his youthfulness barely hidden these days by a silvery patrician goatee.’
      • ‘They keep my energy levels up and ensure my youthfulness.’
      • ‘Zeffirelli used young inexperienced actors, Olivia Hussey (Juliet) and Leonard Whiting (Romeo), giving the action its visual youthfulness but losing poetic weight in the lines.’

Pronunciation

youthfulness

/ˈjuθfəlnəs//ˈyo͞oTHfəlnəs/