where·by /-ˈbaɪ/
(ad.)憑什?;為何;因此
Where·by adv.
1. By which; -- used relatively. “You take my life when you take the means whereby I life.”
2. By what; how; -- used interrogatively.
Whereby shall I know this? --Luke i. 18.
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whereby
adv 1: as a result of which
2: by or through which; "the means whereby we achieved our
goal"