A window or small window-like opening, especially one found in anatomy or architecture.
Latin 'fenestra' meaning 'window,' possibly derived from Proto-Indo-European roots relating to light and visibility; the word has been used in medical and architectural terminology since ancient times.
Your inner ear has two fenestrae—the oval window and round window—and without these tiny openings, sound couldn't reach your hearing nerves, so you literally couldn't hear without them!
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