Roger Woodham replies:yet,still,already-position and use

Yet - position in sentence

I would say that your grammar book, Cambridge Dictionaries and the British Library are all correct, Maria-Leena.

Yet
is normally placed at the end of the clause, particularly in informal English and in questions, but can go immediately after not in negative sentences in a more formal style, such as Cambridge Dictionaries and the British Library have used. Compare also the following:

Although she has been in Britain for more than a year, Maria has not yet visited either Wales or Scotland.

Yet - meaning and use

We use yet in questions to ask whether something has happened up to the present time. Not yet then indicates that it hasn't happened yet:

In a more formal style it is possible to use yet in affirmative sentences:

In a less formal style, we might say:

Thus, in negative sentences, as we can see from these examples, there is considerable overlap in meaning and use between yet and still. Still is the more emphatic of the two.

still - meaning and use

We use still in questions, affirmative and negative sentences to indicate that something is not finished and that we are perhaps surprised or concerned about this. Because it is emphatic, it often carries considerable word stress:

already - meaning and use

Whereas still and yet normally refer to present and future circumstances, already normally refers to something that is in the present or recent past. It is mainly used in questions and affirmative sentences and usually expresses surprise that something has happened sooner than expected.

still / already - position in sentence

Note from the above examples that in contrast to yet, still and already usually occupy mid position in the clause.