Step-by-step explanation:
(a) Young - Youth
(b) Dark - Darkness
(c) Wide - Width
(d) High - Height
(e) Wise - Wisdom
(1) True - Truth
In those cases, the abstract noun is formed from given adjectives. They can be formed by adding suffixes such as the suffix 'ness' but usually, there is a lot of abstract nouns that are formed without using any suffixes or prefixes. They can be learned.
- An abstract noun is considering an idea or state such as examples from the above: ''Width, Youth, Truth'' and more.