Omittance is a word that means the act of omitting, or leaving out. Synonyms for omittance include omission, exclusion, neglect, oversight, and skip. These words all convey the same meaning of not including something or someone in a particular situation or action. Omission specifically refers to leaving something out intentionally or unintentionally. Exclusion implies purposely excluding someone or something from a group or event. Neglect suggests that something has been neglected or overlooked due to lack of attention. Oversight implies a mistake or oversight in omission. Skip denotes intentionally not doing something or leaving it out. Overall, these synonyms all convey a sense of something not being included, whether intentionally or unintentionally.