Submitted by lys on October 3, 2010

thus, therefore and hence are different

A simple way of distinguishing and using these words accurately:

1. ‘Thus’ means ‘in this/that way’ - it relates to ‘HOW’ - the manner in which - this or that happens or comes about. It has a practical flavour. eg.Traditionally, you arrange things thus = Traditionally, this is how you arrange things

2 .’Therefore’ means ‘for this reason’, or ‘because of this or that’ - it relates to deductive reasoning, it tells WHY this or that is so, or happened. eg. He was late and therefore missed the bus = he was late and for this reason missed the bus

3. ‘Hence’ means ‘from this/that’ - it relates to WHERE - position, or point in time; it tells from where or what, or to where or what, something comes, derives, or goes eg. -i. Get thee hence! = Get yourself away from here! -ii. Henceforth all entrances will be guarded = From now on all entrances will be guarded -iii. She got the job - hence her good spirits = She got the job and her good spirits derive from that fact. (Note the different slant to ‘therefore’, which would also fit, but would say ” her good spirits are due to (’because of’; ‘for that reason’) that”.

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I was shot in the leg, hence my limp.

I think therefore I am, I think.

Thus was the wrath of the lord visited upon Sodom and Gomorrah.

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Thank you :-)

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Thanks guys this was helpful

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both - and; either - or. Take your pick. Forgive other punctuation and syntactic errors and omissions; the cause of which, I assure you, was haste.

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What a bunch of purist nonsense! Check your dictionary, thus can either be used in the manner you state and as a synonym for therefore. Therefore, thus and hence, it can be used in the same manner therefore is used, and, indeed, in its stead.

Also it's thus, not thusly, as healyjake incorrectly corrected you.

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Sorry, this is going to sound like a lesson, but I am a teacher, and I write a language blog for foreign learners, so that’s how I’m used to doing it. (In fact this has given me an idea for a blog post). This is what I would tell my students:

1. The most common way to talk about result is to use ‘so’. In this meaning (‘as a result’), ’so’ is a conjunction and usually follows a comma:

“He enjoys his job and the salary is good, so he is reluctant to think about moving.”

2a. In more formal language we can use ‘therefore, consequently, thus' and 'hence' with the same meaning as ‘so’. They are adverbs and normally start a new sentence, although 'therefore' and 'consequently' can follow a semicolon and are usually followed by a comma:

“He enjoys his job and the salary is good; therefore / consequently, he is reluctant to think about moving.”

“He enjoys his job and the salary is good. Thus / Hence he is reluctant to think about moving.”

2b. Alternatively, all four can be used after a comma when combined with ‘and’:

“He has both an enjoyable job and a good salary, and therefore / consequently / thus / hence, he is reluctant to think about moving.”

2c. In this sense, despite what lys says, I believe (and dictionaries suggest) all four words to be interchangeable with little or no difference in meaning, the only real difference being in formality. In the dictionary entries below, 'thus', 'hence' and 'consequently' are all marked as synonyms of 'therefore'.

3. ‘Hence’ and ‘thus’ (but not ‘therefore’ or ‘consequently’) can be followed by a noun or noun phrase instead of a clause, in which case they normally follow a comma. In fact 'hence' is usually used like this, but a subject-verb clause is also possible. The meaning is virtually the same ('as a result of this'):

“He enjoys his job and the salary is good, hence / thus his reluctance to think about moving.”.

4a. ‘Thus’ can also be used to mean ‘in this way’, and in this meaning is interchangeable with ’thereby’. They are often followed by an -ing form (present participle):

“He has been given a large salary increase, thus / thereby enabling him to buy a larger house”.

4b. 'Thus' with the meaning of 'in this way' or 'like this' can also be used at the end of a sentence - "You slide the paper in thus", "I spoke to him thus".

5. Hence literally means ‘ from here’, as in “ Get thee hence!,” but like the rest of its family - ‘thence, whence, hither, thither’ and ‘whither’ is not used like this much in modern English. But we do use it to mean "from now " in idiomatic expressions like “Ten years hence”, and the words "henceforth, henceforward".

6. Although those expressions do indeed refer to the future, I can't remember having seen anything suggesting that ‘hence’ in the meaning of 'as a result' only refers to the future or that ‘thus’ only refers to the past. Both these sentence seem fine to me:

“Sales have been good this year and thus we’ll be able to pay out larger bonuses than expected.”
“He spent his formative years in India. Hence his extensive knowledge of Indian culture.”

My problem with lys is that he seems to think that a word like 'hence' or 'thus' can only have one meaning. But dictionaries give these two words at least two meanings each. As far as I'm concerned, in his example sentence - "He was late and therefore missed the bus", any of the other three words (or indeed 'so') could substitute for 'therefore' without any change in meaning (although I'd accept that of the four, 'therefore' is the most natural-sounding).

http://www.merriam-webster.com/dictionary/hence
http://www.merriam-webster.com/dictionary/thus

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@Alexander - I more or less agree with your definition of 'thereby', although I'd tend more to 'in this way, in this manner'. But the use in your examples is not how I understand the way we use thereby:

My own version of your example might go something like:

"After weeks of intense debates, the delegates finally came to an accord and signed the Nuclear Disarmament Treaty, thereby establishing a framework for the next round of disarmament."

Here are example sentences from various dictionaries:

"Regular exercise strengthens the heart, thereby reducing the risk of heart attack."

"Diets that are high in saturated fat and cholesterol tend to clog up our arteries, thereby reducing the blood flow to our hearts and brains."

"The aim of the military action was to open the roads to Sarajevo and thereby end the capital's 40-month siege."

"He signed the contract, thereby forfeiting his right to the property."

In each case it means 'in this way'. You could no doubt substitute therefore in all these examples, but I think the meaning would be slightly different - it would simply mean 'consequently'. But interestingly, I think you could replace 'thereby' in all these dictionary examples with 'so', which seems to be able to mean both 'therefore' and 'in this way'.

And I'm afraid I don't think using 'therefore' in your examples make an awful lot of sense:

"After weeks of intense debates, the delegates finally came to an accord and signed the Nuclear Disarmament Treaty, which therefore calls for the immediate and complete abolition of nuclear arms."

Sorry, but I don't really get the logic here. 'The Treaty simply calls for the 'immediate end ...'. It doesn't call for this because the debates came to an end or because the delegates signed the accord. Personally, I wouldn't use either 'thereby' or 'therefore' here.

And I don't think this one works either - "This thing is a balloon, thereby it is made of rubber". My dictionary defines 'thereby' as being - "used to introduce the result of the action or situation mentioned". A balloon is not made if rubber as a result of it's being a balloon, surely? Isn't that putting the cart before the horse?

Sorry to be a bit negative ;), but I think there is a clear difference between 'thereby' and 'therefore'.

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Interesting point Irvin, about the word "Thereby". Nowadays, it seems that it has become increasingly replaced with the word "Therefore". They are oftentimes used interchangeably, however, there does appear to be a difference between their definitions.

"Therefore" means "For that reason", whereas "Thereby" means "By that means" or "Because of that".

After contemplating many various examples, I cannot think of a specific case in which the use of one of the adverbs is favored over the other. In every example, it appears that both words can be successfully interchanged. I would love to see an example that proves otherwise. More often than not, I'm fairly sure that it comes down to the individual writer to determine which of these words, along with hence, thus, etc., sound or look more aesthetically pleasing.

Ex: After weeks of intense debates, the delegates finally came to an accord and signed the Nuclear Disarmament Treaty, which thereby calls for the immediate and complete abolition of nuclear arms.

(I thought I had just thought of one, but I guess "therefore" also works here. However, I feel that "thereby" looks more formal, which appeals to the context, and sounds slightly better than "therefore". Although, grammatically speaking - both are explicitly correct.

And just to be a certified grammar nerd, in reference to your example, "I'm broke, hence I will walk rather than taking the bus."; "taking" should actually be replaced with "take". ;)

Furthermore, for the last part. Wouldn't it sound even better if that sentence became "This thing is a balloon, thereby it is made of rubber"? Basically remove the "and" while adding the "it". Moreover, replacing "thereby" with "therefore" in this example still works perfectly. And for some reason, I think "therefore" sounds better in this case. Any thoughts?

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It sounds weird to me some stuff you wrote. As far as I know, "Thus" is used for conclusions in the past. Ex. The troops fought to a standstill, thus no winner was declared.
Unlike "Hence" which is used for future. Ex. I'm broke, hence I will walk rather than taking the bus.
Don't forget the word "Thereby", which is very important as well. In the case: ": This thing is a balloon, and thus is made of rubber and inflates when you blow into it." It would sound better if we say "...and thereby is made of rubber..." since "Thereby" means "Because of...". But I'm not sure. What do u think?

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Thus: This thing is a balloon, and thus is made of rubber and inflates when you blow into it.

Therefore: This thing inflates when you blow into it and is made of rubber; therefore, it is a balloon.

Hence: This thing is called a balloon, hence it must inflate and be made of rubber.

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Still non the wiser. Wish I was intelligent.

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It is very useful information that clears up the concepts (synonymous English words) and their minor difference in English writing.
Thanks to the editor for sharing this information.

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True. Thus is usage clarified.

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It should be "You arrange things thusly." Thus modifies the verb "arrange" here and is therefore behaving as an adverb.

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