A colleague told me today a very nice definition for a PhD work:
“Doing a PhD thesis is a lonely task that cannot be carried out alone”
I couldn´t agree more (unfortunately I don’t know who is the author of the sentence, if you do let me know and I´ll give the corresponding credit).
A perfect complement to the previous sentence is the following reply from Carles Farré:
“A PhD student’s paper is an individual work with many authors”