All 6 Uses

however
in
For Esme:--with Love and Squalor
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The young lady, however, seemed slightly bored with her own singing ability, or perhaps just with the time and place; twice, between verses, I saw her yawn.†

however = a word used to connect contrasting ideas as when using though, in spite of that, in contrast, nevertheless, etc.
My guest, however, calmly moved her chair an inch or two so that her back broke all possible further communication with the home table.
*

however = though (used to connect contrasting ideas)
He thought if he wrote a letter to an old friend of his in New York there might be some quick, however slight, therapy in it for him.
*

however = regardless of how
However, I've since discussed the matter rather extensively with my wife, a breathtakingly levelheaded girl, and we've decided against it—for one thing, I'd completely forgotten that my mother-in-law is looking forward to spending the last two weeks in April with us.†
All through the war, Clay had read all Loretta's letters aloud to X, however intimate they were—in fact, the more intimate, the better.†
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However I have thought of you frequently and of the extremely pleasant afternoon we spent in each other's company on April 30, 1944 between 3: 45 and 4: 15 P. M. in case it slipped your mind.†

Definitions:

(1) (however as in: However, complications may...)
though (or another expression that connects contrasting ideas)

Based on idea 1 we might not expect idea 2, but this is a way of saying that even though idea 1 exists, we still have idea 2. Synonyms include in spite of that, despite that, nevertheless, nonetheless, on the other hand, in contrast and but.
(2) (however as in: However much she tried...)
to whatever degree (regardless of how much; or whatever unspecified amount)
(3) (however as in: However you do it, get it done!)
in whatever way
(4) (meaning too rare to warrant focus)
Much more rarely (and arguably incorrectly), however can be used to intensify the word how, as when one says "However did you find her?" Grammarians would suggest using two words for that usage: "How ever did you find her?"