This is not accurate, Caloni. Generally speaking, the plural -ões is used as a rendering of Latin plural -ones of the third declension (in the accusative case, of course, from which almost all Latin nouns of the Portuguese language came from). Examples:
lat. nom. sing. definitio:
lat. acc. sing. definitionem => port. sing. definição
lat. acc. pl. definitiones => pot. pl. definições
lat. nom. sing. ratio:
lat. acc. sing. rationem => port. sing. razão
lat. acc. pl. rationes => port. pl. razões
This is a general rule for all "abstract" nouns derived from Latin words that ended in -onem/-ones, a pair that always correspond to -ão/-ões in Portuguese.