名詞 aperture:

1. a device that controls amount of light admitted
2. a natural opening in something
3. an man-made opening; usually small

1. A separation, an aperture, a fissure, or a short passage in an organ or a body part.
   裂孔，孔器官或身體部位中的孔隙、隙縫、裂隙或通道
2. A lid or flap covering an aperture, such as the gill cover in some fishes or the horny shell cover in snails or other mollusks.
   鰓蓋覆蓋在一孔或縫隙上的蓋，如一些魚類的鰓或覆蓋在蛇或其它軟體動(dòng)物身上的角質(zhì)殼
3. What aperture are you using?
   你使用多大的光圈?
4. The aperture in the door is so wide.
   門上的孔隙太大了。

ap.er.ture

n.（名詞）
An opening, such as a hole, gap, or slit.
孔，洞：開口，如洞、縫隙或缺口

A usually adjustable opening in an optical instrument, such as a camera or a telescope, that limits the amount of light passing through a lens or onto a mirror.
光圈：光學(xué)儀器上的一個(gè)可調(diào)開口，如照相機(jī)或望遠(yuǎn)鏡，它控制穿過鏡頭的或到鏡面的光的數(shù)量
The diameter of such an opening, often expressed as an f-number.
孔徑：這種開口的直徑，常以f數(shù)表示
The diameter of the objective of a telescope.
孔徑：望遠(yuǎn)鏡物鏡的直徑

來源：
Middle English
中古英語
from Latin apertôra
源自 拉丁語 apertôra
from apertus [past participle of] aperore [to open] * see wer- 4
源自 apertus [] aperore的過去分詞 [開，打開] *參見 wer- 4

【引伸】
ap.ertur.al
adj.（形容詞）