In the sentence: Dog is "an" or"a" universal term for a fluffy creature, should it be "a" or "an"

How do you pronounce 'universal' ?

Is it un - iversal ?
or
YOU - niversal ?

The rule works on how the word is pronounced, not just on the first letter. So 'universal' and 'university' is 'a', as those two words sound start by sounding like like 'yoo', not 'un'.

Similarly, 'an' hour, as the 'h' is silent and is pronounced 'our'.

It's "a dog."

Universal is pronounced: you-knee-VER-suhl; tonic stress on the VER.