considerable, enormous (esp. BrE), lengthy, long, major, serious, significant, substantial
After a considerable delay, the government has agreed to accept the recommendations.

five-minute, six-month, two-hour, etc.
excessive (esp. BrE), inordinate (esp. BrE), undue (esp. BrE), unnecessary
Undue delays have been caused by people not doing their jobs properly.

inevitable, unavoidable
brief, short, slight
minimal, minimum
unexpected, unforeseen
frustrating
costly
bureaucratic
The building project has been plagued by bureaucratic delays.

further
airport, flight, traffic, travel
time
There is a five-minute time delay on the bank's safe.

series
After a series of lengthy delays, the case finally came to court.

be subject to (esp. BrE)
Flights to New York may be subject to delay.

be plagued by, encounter, experience, face, suffer
Passengers have experienced long delays.
The project has been plagued by delays.

cause, lead to
The strike has led to some delays in train services.

avoid, eliminate, minimize, prevent, reduce
Please address your letters properly so as to reduce delays.

apologize for
I apologize for the delay in replying to you.

occur
Passengers complain about lack of information when travel delays occur.

without delay
Please send him the information without delay.

delay in
delays in getting to the airport

delay of
a delay of several weeks

delay to
further delays to the plan

seriously, significantly, substantially
Mellanby's arrival was seriously delayed by a late train.
These drugs can significantly delay the onset of the disease.

indefinitely
further
unduly (esp. BrE)
temporarily
slightly, somewhat
deliberately

Delay is used with these nouns as the object:
announcement, arrival, completion, decision, delivery, departure, development, election, entry, execution, flight, implementation, introduction, launch, legislation, onset, payment, publication, recovery, reform, release, retirement, return, vote