Breakup

The word "breakup" is an idiom. It is when an intimate relationship ends. The term is not used for relationships that end because of death. Marriages which end are not normally called breakups.
Reasons.
A breakup can happen when one person is unhappy in their relationship. If a person ends a relationship, that person "dumps" their partner.
Some relationships end because both people are unhappy. The breakup is then "mutual".
People in a relationship may be unhappy because of differences in:
Grief.
After a breakup, people may feel grief or unhappiness. Their personality or "sense of social value" may change.
People may need "time to heal" after a breakup. This time can depend on the length of the relationship.
Statistics.
eNation did a survey on breakups in 2008. Almost one in three Americans were in a breakup within the last ten years. Young people were more likely to have been in more than one breakup.