Which final stable syllable is used in words expressing a belief or state of being?

The final stable syllable that is used in words expressing a belief or state of being is -ness. This suffix is commonly added to adjectives to form nouns indicating a state, quality, or condition. For instance, when "happy" is transformed to "happiness," it conveys the state of being happy.

This characteristic makes -ness particularly relevant for expressing several beliefs, qualities, or states such as "kindness" (the state of being kind) or "weakness" (the quality of being weak).

While -ment can denote the action or result of a verb, it doesn't specifically capture the essence of belief or state in the same way. The suffix -tion typically converts verbs into nouns but focuses more on processes or results rather than personal beliefs or states of being. Likewise, -ure relates more to the result or process of certain actions and does not directly signify a state or belief. Thus, -ness is clearly the appropriate suffix for the context of expressing beliefs or states of being.