14/07/16 The Uses of ‘SO’ & ‘THEN’

So and then can both be used to mean “since that is so.”  There is a slight difference. Then is most often used when one speaker replies to another: it means “it follows from what you have said.” We do not normally use then when the same speaker wants to connect two ideas (“It follows from what I have said”). So can be used in both ways.

Compare:

• It’s more expensive to travel on Friday, so I’ll leave on Thursday evening. (NOT … Then I’ll leave on Thursday evening.)
• It’s more expensive to travel on Friday.” “Then/So I’ll leave on Thursday evening. Thanks for the advice.”
• I’ll be needing the car, so you’ll have to take a taxi.
• I’ll be needing the car.” “Then/So I suppose I’ll have to take a taxi.”