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I have seen a few Q&A's with this title but none really reflects my question. I am aware both are adverbs and so forth and how they syntactically can be used equivalently, but what about connotations? Are there places where "therefore" is preferred over thus and vice versa? Are there any fine differences in usage?

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And then there's hence ... – hippietrail Nov 28 '14 at 17:24

Therefore is used in introducing a conclusion that follows from what has been said previously.

You are drunk, and that makes you incapable of operating machinery. Therefore you shouldn't fly a plane.

Thus means in this way. For example:

He waved his arms around thus. (speaker waves arms around in demonstration)

Extending that meaning, it can be used to introduce the intended consequences of an action:

I intend to eat less, and thus lose weight.

And stretching that meaning further it can, like therefore, indicate the conclusion of an argument:

Trees are plants, and plants are living. Thus we can see that trees are living.

To me at least, in the cases where they have the same basic meaning, the effect of therefore and thus is slightly different: therefore emphasises that the conclusion is an inescapable logical consequence of what goes immediately before; thus puts more focus on the argument as a whole and the way it leads towards the conclusion.

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+1, and damn your eloquence! ;-) – Robusto Jun 21 '11 at 13:57
Brilliant. I googled the difference because I had a feeling that each word emphasised an argument and its conclusion in different ways, but I couldn't quite put my finger on it. Your explanation, however, was just perfect. – André Terra Apr 30 '14 at 14:08
It seems to me that it should be He waved his arms around thusly. Perhaps that is a dialectal difference ´_? Also, what does "thus" mean in thus far`? I would say it means something different than "in this way". Comments? – macmadness86 Aug 4 '14 at 9:34
@mac Thus and thusly are equivalent when the meaning is ‘in this way’. Thusly arose in the 18th or 19th century as a hypercorrection (like saying “He runs fastly” instead of “He runs fast”), but is now generally considered fairly standard. – Janus Bahs Jacquet Mar 25 '15 at 10:14

From American Heritage Dictionary of the English Language, Fourth Edition


  • In this manner: Lay the pieces out thus.1
  • To a stated degree or extent; so. 2
  • Therefore; consequently: Thus3 it was necessary for me to resign.
  • For example: Few of the nation's largest cities are state capitals; thus4 neither New York nor Chicago is the seat of its state's government.

1 not same: you cannot say lay the pieces out therefore.
2 not same: you cannot say we've discussed three topics therefore far
3 this meaning is the same
4 not same: replacing it with therefore makes it a conclusion out of an example.

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What about the instances where 'therefore' can be used but 'thus' cannot? – Mitch Jun 21 '11 at 13:45
@Mitch, on that side it is much more simple as therefore has only "1. For that reason or cause; consequently or hence." – Unreason Jun 21 '11 at 13:50

I am going to take a swing at this, because I just had a nice conversation with an Austrian about it. We came to the conclusion that the German ways of expressing them could be summarized like this:

folglich/in folge -> thus

deshalb -> therefore

It is raining (A), therefore the grass is wet (B).

  • therefore emphasizes that A was the cause of B.

It is raining (A), thus the grass is wet (B).

  • thus means that A results in B, but does not emphasize that A was the cause of B.

also see:

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Neither thus nor therefore is used in matrix clauses with if-conditionals. – Janus Bahs Jacquet Mar 25 '15 at 10:18
@JanusBahsJacquet First of all, you clearly don't know about Aristotle's syllogism (I suggest you do some reading. Secondly, my examples were minimalistic for the purpose of emphasizing the differences. See en.wikipedia.org/wiki/Hypothetical_syllogism – macmadness86 Mar 25 '15 at 10:24

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