i SUFFIX
makes abstract noun of the verb; place/instrument/result of verb action;
deci.is N 2 2 LOC P N
deci.is N 2 2 DAT P N
deci.is N 2 2 ABL P N
decet, decere, decuit, - V (2nd) IMPERS [XXXBO]
it is fitting/right/seemly/suitable/proper; it ought; become/adorn/grace;