All 3 Uses

therefore
in
Hiroshima, by John Hersey
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She said she had some luggage and her children were sick — they were still vomiting from time to time, and so, for that matter, was she — and therefore she feared she could not.†
Chpt 2 *

therefore = for that reason
The class of people to which Nakamura-san belonged came, therefore, to be called by a more neutral name, "hibakusha" — literally, "explosion— affected persons."†
Chpt 5
Take therefore no thought for the morrow: for the morrow shall take thought for the things of itself.†
Chpt 5

Definitions:

(1) (therefore)
for that reason (what follows is so because of what was just said)
(2) (meaning too rare to warrant focus)