In Spanish, a hiatus refers to the occurrence of two vowels that are next to each other but belong to separate syllables, meaning that they are pronounced in separate beats.
Hiatus is typically avoided in Spanish through the use of accent marks. However, there are instances where a strong vowel without an accent (a, e, o) is followed by a weak vowel with an accent (í, ú).
Here are some examples:
poesía (poetry)
país (country)
estrés (stress)
alcohol (alcohol)
In these examples, the strong vowels 'o' and 'a' are followed by the weak vowels 'í' and 'í,' respectively, creating a hiatus. The accent on the weak vowel indicates that it should be stressed, and therefore, the hiatus is allowed in these cases.