In Situ, In Real Time

These two expressions are used in both hyphenated and non-hyphenated form. Which do you use when?

In situ is a Latin expression meaning “in the place.” When used as an adverb, there is no hyphen; when used as an adjective, there is a hyphen.


The microbes for the project will be cultivated in situ. (adverb telling where cultivated)

The field will be developed using in-situ combustion. (adjective modifying combustion)

Similarly, real-time is hyphenated when used as an adjective, and not hyphenated when used as an adverbial phrase with the preposition “in.”


Fiber-optic cable enables temperature measurement in real time. (adverbial phrase telling when measured)

Real-time data are essential for directional drilling success. (adjective modifying data)

How shall we remember this?

If there is a noun right after it, hyphenate it. If not, don’t.


2 Responses to “In Situ, In Real Time”

  1. Daniel Lieberman Says:

    interestingly, you use another confusing term IN YOUR EXAMPLE: fiber optics. This term is also often used with a hyphen. I would suggest that – because you use the term as an adjective – it should be fiber-optics.

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