Hiatus (derives from Latin hiatus, -us, m.: gap; cf. hiare, hio, hiavi (hisco); (χαίνω) έ-χαν-ον, κέχηνα; Old High German ginēn; German 'gähnen' -> "yawn") is

1. a linguistic term. It describes a pause between same vowels at the end and the beginning of a word, as in "co'operation".
2. a gap in geological strata.
3. a fissure in a bone.
4. a small difference in pitch between two musical tones, cf. Interval (music)