uh-oh
Synonym discussion
Sense: exclamation/1
All three express a reaction to a problem, but they differ in tone and severity. 'Uh-oh' is the most neutral — it works for anything from a spilled drink to a sudden danger. 'Oops' is lighter and suggests a very small, often funny mistake (e.g. typing the wrong key). 'Whoops' is similar but sounds slightly more playful or childlike. 'Oh no' carries disappointment or worry, usually for something more serious than 'uh-oh' would cover. For example: 'Uh-oh, I forgot to buy eggs' sounds matter-of-fact, while 'Oh no, I forgot to buy eggs' sounds upset.
Etymology
An onomatopoeic expression formed by combining the hesitation sound 'uh' with the realization sound 'oh'. It imitates the natural change in a person's voice as they notice that something is wrong. First recorded in English in the early 1900s.