The phrase "a single existing" is correct and usable in written English.
It can be used when referring to one specific item or entity that is currently present or in existence.
Example: "In the vast library, there was a single existing manuscript that had never been published."
Alternatives: "one existing" or "a solitary existing".
"I saw that on October 7th, Putin's birthday, there isn't a single existing holiday anywhere in the world," he says.
There is no loop in a Cayley tree, so each site can only be connected to a single existing cluster site, by a single link.
Because of the structural and functional varieties of the included articles, it was a difficult task to find a single existing assessment method which could be applied to all papers.
Even though there have been attempts to scale relational databases horizontally, on the contrary, RDBs are designed to scale vertically by means of adding more power to a single existing server [3].
If the algorithms are being developed to analyse a single existing dataset, then the development time is important as it is likely to form a significant proportion of the project as a whole.
1. Make sure state and local governments don't lay off a single worker or cut back a single existing program.
As long as the occlusion times are short enough, babies will construct a representation of a single continuously existing object over discontinuous motion.
FD2 is akin to Gottlob Frege's theory of definite descriptions; but whereas Frege chose a single arbitrary existing object to serve as the conventional referent for empty singular terms, FD2 makes this object non-existent.
Finally, even though nature abhors a vacuum [56], in this paper I consider a single species existing in a single patch.
The other eight alleles exhibited a segregation pattern characteristic of a single mutation existing on a nuclear chromosome.
In particular, we should stress here that dividing space into N compartments is equivalent to replacing a single species existing in (inhomogeneous) space with N species living in a well-stirred mixture (each species being the population of a bin).
