The dash isn't needed when you prefix "h" to a vowel (because native Irish words never begin with "h" in their basic form, there is no confusion): go hálainn, go hiontach But when you capitalise these words, the "h" remains in lower case: Go hÁlainn, Go hIontach When "t" or "n" are prefixed to a vowel, on the other hand, you need a dash: an t-éan, na n-éan When capitalised, the dash is not used: An tÉan, Na nÉan