Unexpected is what was not provided : that is, it could not be seen, detected or known in advance. The unforeseen, therefore, surprises .
By example : “I liked the unexpected end of the movie as it escapes the usual”, “This month we had several unforeseen expenses and the truth is that we ran out of money”, "The unexpected encounter moved the woman, who did not expect to meet her ex-partner at the party".
It is common to encounter unforeseen situations or events in everyday life. Suppose a person traveling by train to your workplace, upon arrival at the station, that the service is running with a delay of half an hour due to a accident That was registered hours before. This unforeseen makes me end up being late for his job, since he had not anticipated that contingency and therefore he did not leave his house in advance.
A man who had promised to take his daughter to a park may be forced to cancel the plan since his boss asks him to stay a extra time in the office to complete some pending tasks. In order not to have a labor problem, the subject complies with the request: in this way, the unexpected prevents him from enjoying a date with his daughter.
A mechanical failure in a car that had not given any previous signals, a power outage for the sudden explosion of a transformer and a visit to the doctor after suffering a blow in the head for slip on the street are other unforeseen situations that may force changes to be planned.