Almost Vs Nearly

1. 'Nearly' and 'Almost' have similar meanings, and in many cases the can both be used without much difference. Usually, 'almost' is used to mean that something is a little 'nearer' than 'nearly'. E.g. So at 12:15 we might say 'It is nearly lunchtime', and at 12:27 'It's almost lunchtime'. 

We are nearly there.             We're almost there. 

S/he is nearly six feet tall.     She's almost six feet tall. 

I nearly as clever as you.         I am almost as clever as you. 

I nearly fell off my bike.          I almost fell off my bike. 

2. Typical mistakes: 

My aunt's got a strange way of talking. She nearly sounds foreign. 

It is nearly incredible. 

I nearly think you're right. 

Our cat understands everything - he's nearly human. 

In these sentences, we are not talking about progress towards an end (people do not get more foreign; cats do not get more human), or about thinks that are easy to measure. In cases like these 'almost', not 'nearly', is used. 

Our cat understands everything - he's almost human. 

I almost think you're right. 

It's almost incredible. 

My aunt almost sounds foreign. 

In that long dress she looks almost graceful (Not: ...nearly graceful). 

Note that 'nearly' is not often used with 'never', 'nobody', 'no-one', 'nothing', 'nowhere', 'no' and 'none'. Instead, we used 'almost', or we used 'hardly' with a non-negative form. 

Almost no money     hardly any money 

Almost nobody         hardly anybody 

Almost never             hardly never