Punctuation to introduce a list: comma vs. colon vs. nothing
Which of these sentences is written correctly?
- Angela has three brothers, Mark, Adam, and Ryan.
- Angela has three brothers: Mark, Adam, and Ryan.
- Angela has three brothers Mark, Adam, and Ryan
Angela has three brothers: Mark, Adam, and Ryan.
That's the one to go with.
N.B. This is called the syntactical-descriptive function of the colon: it "introduces a description—in particular, makes explicit the elements of a set" (Wikipedia)
Angela has three brothers: Mark, Adam, and Ryan.