Some nouns have one meaning in the singular and another in the plural:
a. Advice = counsel / advices = information
b. Air = atmosphere / airs = proud
c. Authority = command / authorities = persons in power
d. Good = wise / goods = property
e. Iron = metal / irons = fetters, chains
f. Force = strength / forces = army
g. Content = satisfaction / contents = things contained
h. Respect = regards / respects = compliments
i. Work = job / works = compositions, factories