Severity is a term used to describe the intensity, harshness or seriousness of an event or condition. Synonyms for it could include harshness, intensity, rigor, gravity, seriousness, sternness, or austerity. Other Terms like acuteness, bitterness, strictness, bleakness, inclemency, rigidity, stringency, and unyieldingness could be substituted.
The word "severeness" can be used in different contexts such as in the environment, where it could refer to the severity of a natural disaster or climate change. In medicine, it could be used to describe the severity of an illness or injury. In an educational context, it could refer to the severity of punishment or discipline for violating school rules.
In summary, a variety of words can express similar meanings to the term "severeness." The context of the term will determine which synonym best suits the text.