1. The position of Chairman is tenable for a maximum of three years.
tenable = capable of being justified, capable of being held
No, this is not a use for the work "tenable." Tenability is a property of opinions or ideas -- particularly ideas of a speculative or philosophical nature (as opposed to concepts concerning concrete empirical reality.)
An idea can be "held" mentally -- not relinquished, stuck with in the face of contrary opinions, or just "occurring in the mind."
> He held many unusual political points of view -- most of them not tenable.
> He held that women make better astronauts than men because of their smaller size, and NASA agreed that this was a tenable position.
> He always held that Emma is a finer novel than Pride and Prejudice, a tenable view in the eyes of his Professor.
But a job is not said to be "tenable."
> The Chairman's economic theories of business were barely tenable, according to the dissatisfied members of the Board of Trustees.
> The position of Chairman can be held for a maximum of three years.
2. An opinion untenable by those who know the facts.
untenable = unacceptable
"Untenable" does not mean "unacceptable" exactly. It means that the opinion is not sustained or supported or justified by the facts of the matter.
> The woman decided that her boyfriend's views on household money management were unacceptable to her.
This means that she disagreed with his views, that she did not want to comply with them. It does not make a statement one way or the other about the worth or factual merit of his ideas, only that the woman rejected them (for whatever reason) in principle.
> His opinions about the artistic merit of her poetry were untenable.
This means that his ideas were not sustained by reality, that the actual facts of the matter were insufficient to uphold his point of view. There is no special idea that his opinions were "unacceptable" and needed to be rejected in principle, only that they were unjustified under the circumstances.
> Their ideas about racial equality were both untenable and unacceptable.
This means that the ideas were unsupported by the facts AND that the ideas should be rejected in principle.
2. He was detained by business.
3. Don't let me detain you.
4. Something detained him.
detain = to keep from proceeding
Yes, "kept from proceeding" in the sense of being stuck in one place, unable to leave and go elsewhere.
Children who misbehave in school are given "detention" -- an enforced period after school when they cannot leave the detention hall, but must stay in that place until they have served their sentence.
7. The whole scheme came unstuck
come unstuck = ruined
Something that has come unstuck is ruined, but the words are not synonyms.
A building or even a city can be ruined. A book left out in the rain is ruined, as is a suede jacket. But they did not become unstuck.
"Coming unstuck" means "ruined for a specific reason" -- the failure of the plan to go according to expectations. First one thing unexpectedly goes wrong, and then another, and before you know it, the plan is in shambles and can not go forward. When something in the nature of a hitch arises, the worry is that the entire plan will come unstuck.
Certain types of action movies such as Oceans 11 develop suspense by raising the fear that the plan will come unstuck.
8. When her last play flopped she became completely unstuck.
flop = to fail utterly as in: The play flopped.
No. People don't become unstuck; plans do.
People become "unglued" or "undone."
> When her last play flopped, she came apart at the seams. She'd come undone.
> Her last play flopped because her plan to advertise inexpensively came unstuck. When the play did no box office, she became unglued, undone. She fell apart, came apart at the seams, lost it, became a basket case.
> Her last play was about a poor boy's dreams of becoming a millionaire and how his plans came unstuck. When the play flopped, she lost it -- she just came apart at the seams, a total basket case.
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