accidence (n.) Look up accidence at
late 14c., in philosophy, "non-essential or incidental characteristic," also "part of grammar dealing with inflection" (mid-15c.), in some cases a misspelling of accidents, or else directly from Latin accidentia (used as a term in grammar by Quintilian), neuter plural of accidens, present participle of accidere (see accident). The grammar sense is because they change in accordance with use.