hiatus

noun

• A gap in a series, making it incomplete.
• An interruption, break or pause.
• An unexpected break from work.
• A gap in geological strata.
• An opening in an organ.

  "Hiatus aorticus is an opening in the diaphragm through which aorta and thoracic duct pass."

• A syllable break between two vowels, without an intervening consonant. (Compare diphthong.)

  "Words like reality and naïve contain vowels in hiatus."