adverb used to indicate that something is regrettable or unfortunate
preposition unfortunately can be used as a preposition in some cases to indicate a negative or unfortunate circumstance
Unfortunately, the data was inconclusive and further research is needed.
Unfortunately, the patient's condition has worsened and surgery is now necessary.
Unfortunately, the school budget cuts have led to fewer resources for students.
Unfortunately, the defendant's alibi was proven false, leading to a guilty verdict.
Unfortunately, we are currently experiencing higher than normal call volumes.
Unfortunately, our proposal was not accepted by the client.
Unfortunately, we have grown apart and it's time to move on.
Unfortunately, the deadline for submitting the manuscript has passed.
Unfortunately, the patient's condition has not improved despite our best efforts.
Unfortunately, the court ruled against our client in this case.
Unfortunately, the test results came back positive for a serious illness.
Unfortunately, the project timeline has been delayed due to unforeseen circumstances.