Sincerity is the feminine noun that means the quality of a sincere person. It is synonymous with frankness, smoothness, goodness.
Sincerity is the character trait or from personality of an individual. It is a virtue that translates into honest, truthful and loyal conduct. Sincerity is saying what you really think, even though it can hurt you.
One of the definitions of sincerity indicates that it is a mixture of weakness and truth. Many people are not sincere because they know that if they lie they can manipulate a person and gain some benefit.
For example, if a friend asks you if you like your new outfit and you say yes even though you think no, that is insincere. However, it is important to emphasize that being sincere is not being crude, it is possible to be sincere without hurting people when we express our opinions.
There is also the white lie, expression in English that in Portuguese means silly lie, little lie, pious lie or lie innocent that consists in a lie with good intention, which is said not to hurt the feelings of another people. Still, it is still a lie and insincerity. One of the most frequent examples is: "I don't want to spoil our friendship", when in reality the person wants to say: "I don't like you".
See too the qualities of a person.
sincerity and honesty
Although they are often seen as synonymous, there are differences between sincerity and honesty.
For example, when a person says, "I confess, I was the one who stole your car," he was sincere because he admitted that he committed the crime. Despite this, she was not honest because she committed an unlawful act, which goes against the moral standards of honesty and decency.