I know that I can't say "I have a doubt" in English. But it is very common to say "tengo una duda" in Spanish. I don't know how I could translate "tengo una duda" in the following sentence, since "I have a question" doesn't fit (or I think so)
:
Tengo una duda: no sé si ponerme el vestido negro o el azul.
Thanks.
