In situ is a fairly daunting and complicated Latin term that is not commonly seen in colloquial use. It is usually taken to mean ‘in its original place.’ It is used in many different fields, such as archaeology, economics and literature.
The literal translation of in situ from Latin to English is ‘in place’ (although some will argue it means ‘in position.’) It can be used as both an adjective and an adverb. Its first recorded use was said to be around 1740.
Despite accepted use in numerous professions, the term in situ has not yet found its way into informal use. This is not to say it would be incorrect, nor is it strictly unacceptable, should it be used in the right sentence or context; just that it isn’t ever really seen.
In situ is used in different situations and contexts for a variety of different professions, but always translates to the same meaning of ‘in place/position.’ Examples of use in a sentence include:
‘The fossil was found in situ.’
(Archaeology: The term used here means that what was uncovered was found in the original position that it was made or deposited.)
‘Bob undertook his testing in situ.’
(Psychology: Meaning that the subject of an experiment was located outside of a laboratory or usual work setting at the time, i.e. at the workplace.)