F-number
n. 数, 光圈数
🧩 词语组成解析
🗣️ 情景例句
How long has he held office?
他已任职多长时间了？
No one can match us so far as quality is concerned.
就质量而言，没有任何厂家能和我们相比。
In this way, we have learned all that we know of the laws of astronomy,
例如，用这种方法，我们完全掌握了天文学的规律。