Glancing upward, I saw the aperture, a small blue disk, in which a star was visible, while little Weena’s head showed as a round black projection.
Swinging myself in, I found it was the aperture of a narrow horizontal tunnel in which I could lie down and rest.
Apparently it was considered bad form to remark these apertures; for when I pointed to this one, and tried to frame a question about it in their tongue, they were still more visibly distressed and turned away.
There are no more uses of "aperture" in the book.
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The higher the f-stop, the more closed the camera’s aperture.
It wandered along the crest of the hill and terminated before a fragment of wall pierced by a rough aperture which had once been a door.