The phrase “in detail” is surprisingly often misused. If we look at the phrase in the title above writers will very often write “in details” rather than “in detail”, and we regularly see “in details” appearing in similar phrases in academic writing. So:
Chapter five discusses my results in details.
This research will explore the above theory in details, etc.
For the avoidance of any doubt – in such phrases “in details” is incorrect. It should always be “in detail”. Here “detail” is used uncountably, as it is in the phrase:
She demonstrated attention to detail.
This phrase also always uses detail in the singular (although we could say “she paid attention to the details”).
There is a very similar phrase “go into detail” which can be used in the plural. So:
My earlier chapter touched on this point but did not go into the details.
In this phrase, one could also say “go into the detail”. The distinction here is a fine one: If you say “go into the details”, you are putting the emphasis on the fact that there are several particular points that you will consider. If you say “go into the detail”, you are putting the emphasis on there being, collectively, more that needs to be discussed. This is perhaps a fine distinction, and either phrasing will often be okay.
Some other detailed points about “detail”:
“Detail / details” are minor aspects of a bigger issue. So, “the details will be explained later” (here the same judgement applies as above in terms of whether to say detail or details.
“A detail” has a specific meaning in art – it is a particular small part of a picture that has been singled out so the viewer can see its features more clearly. The picture above is detail taken from a bigger picture of a person’s face.
Detail as a verb means “to list” or “give information”. So:
There are several things we need to consider, as I detail below.
The prosecutor detailed the alleged offences.
Lastly – to confuse matters further – detail has another completely different meaning as “a person or group selected to do a specific task”, or indeed the task itself. This is often used in military parlance. So:
We are the guard detail tonight.
The President’s security detail
This follows through to another verb, meaning given a task.
I was detailed to look after the guests.
Wow! What a lot of detail from just one word…!