definition of "fragment" in FPKM in single end reads

[thinkRNA]

Fragments in FPKM is defined as the fragment of cDNA that is encompassed between a pair of reads in paired end data. However, when the data is single end reads, what is a fragment?

Is it then the next consecutive single end read that makes a fragment or does it converge back to a single read? This is not indicated in the paper either.

[mgogol]

I think the fragment in the case of single reads is just the read, really. The read is from one end of a longer fragment.