Thus Or Therefore?

‘Thus’ or ‘therefore’? There is endless confusion about these two words.
But be warned: the confusion is made even worse by faulty (read, ‘plain wrong’) advice offered on several so-called ‘language learning’ sites.

The difference between the two words is quite straightforward.


‘Thus’ means ‘in this way’ (the ‘how’).

If that’s what you want to say, then use ‘thus’. Chances are you won’t need to use it often. It can sound a little stilted. If it’s used properly, it can be replaced with ‘that’s how’. (So why not say ‘that’s how’?)

I found the combination, manipulated the dial and pulled open the heavy door of the safe; thus (that’s how) I retrieved my treasures.

People often write ‘thus’ when they should write ‘therefore’. The two are sometimes interchangeable but not always.

Which to use, then? ‘Thus’ or ‘therefore’?


‘Therefore’ means ‘for this reason’ (the ‘why’)

It’s often about cause and effect and, in informal language, it can sometimes be replaced by ‘so’.

It was raining; therefore (for this reason), I took my umbrella.

Note that ‘therefore’ starts a new clause, and is preceded a semi-colon, not a comma.
In the example, above, ‘thus’ would be totally wrong. It’s not about ‘how’ you took your umbrella, but ‘why’.

‘Thus’ or ‘therefore’: just check your meaning

Finally, look at these two sentences:

I saw he had a runny nose, a cough and a high fever; thus (that’s how) I decided he had flu.

I saw he had a runny nose, a cough and a high fever; therefore (for this reason), I decided he had flu.

They give you an example of how ‘thus’ and ‘therefore’ seem to be interchangeable – not because they mean exactly the same thing, but because the meaning, or outcome, of the sentence remains the same.

‘Thus’ or ‘therefore’? The simplest advice is, as always, to be absolutely sure about what you mean to say.

Here’s more advice about how to Be Word Wise.