Long variants are simple words inflated with prefixes or suffixes to provide a perception of added value in their inclusion. But because the prefixes or suffixes typically do not add any nuance of meaning, including long variants in your writing dilutes its power and with it its effectiveness. In essence, long variants are another version of wordiness.
The list below contains some common examples of long variants compared with the simple words that convey the same meaning. Simple words convey meaning more clearly and therefore more effectively. This is why the words in the right-hand column are more effective than their listed counterparts in the left-hand column.