Definition of youthfulness in English:
 youthfulness
noun ˈjuːθfʊlnəsˈjuːθf(ə)lnəsˈjuθfəlnəs
mass noun1The fact of being young.
 his relative youthfulness counted against him in business circles
 Example sentencesExamples
-  She delights in flaunting her youthfulness in the face of her older colleagues.
 -  He delights in the youthfulness of his live show crowds.
 -  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.
 -  The average age of participants is about 22.5, so there's no denying their youthfulness.
 
- 1.1 Behaviour or appearance characteristic of young people.
 the eternal youthfulness of Sir Richard was infectious
 Example sentencesExamples
-  Here is Vasiliev at 60, his youthfulness barely hidden these days by a silvery patrician goatee.
 -  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.
 -  These phytonutrients which are powerful in their ability to protect the body and the mind from degeneration and maintain youthfulness.
 -  They keep my energy levels up and ensure my youthfulness.
 -  If you plan to live beyond 70, calcium-rich foods such as milk can help protect your youthfulness.
 
 
  Definition of youthfulness in US English:
 youthfulness
nounˈjuθfəlnəsˈyo͞oTHfəlnəs
1The fact of being young.
 his relative youthfulness counted against him in business circles
 Example sentencesExamples
-  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 Behavior or appearance characteristic of young people.
 the eternal youthfulness of Sir Richard was infectious
 Example sentencesExamples
-  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.