What are some examples of venial sins?
The short answer
The Catechism describes two kinds: sins in a less serious matter, such as hatred that wishes someone only minor evil or abusive language without grave circumstances; and grave matter without full knowledge or consent, such as masturbation when culpability is lessened by immaturity, habit or anxiety.
Lesser matter
Venial sin occurs when, in a less serious matter, one does not observe the moral law (CCC 1862). For example, hatred is a sin when one deliberately wishes a neighbor evil and a grave sin when one deliberately desires him grave harm (CCC 2303). Abusive language is forbidden but is grave only because of circumstances or intention (CCC 2073).
Grave matter, reduced culpability
Venial sin also occurs when one disobeys the moral law in a grave matter but without full knowledge or complete consent (CCC 1862). An example could be masturbation: affective immaturity, force of habit, anxiety or other factors can lessen, even minimize, moral culpability (CCC 2352).