What suffix can change adjectives into nouns?

There are a few suffixes that can change adjectives into nouns, but the most common one is -ness.

Here are some examples:

* Happy (adjective) -> Happiness (noun)

* Sad (adjective) -> Sadness (noun)

* Kind (adjective) -> Kindness (noun)

* Strong (adjective) -> Strength (noun)

Other suffixes that can be used, but are less common, include:

* -ity: Cruel (adjective) -> Cruelty (noun)

* -ty: Brave (adjective) -> Bravery (noun)

* -ship: Friend (adjective) -> Friendship (noun)

* -dom: Free (adjective) -> Freedom (noun)

It's important to note that not all adjectives can be turned into nouns using these suffixes.