This is the 939th most frequent Italian word.
messi
The Italian word "messi" means "placed," "set," or "put" (past participle of "mettere").
Here, 'messo' is used as a past participle in the perfect tense, agreeing with the singular subject 'I' and describing 'placing the books on the desk'.
Ho messo i libri sulla scrivania.
I placed the books on the desk.
In this example, 'messi' describes the files (plural masculine subject) being 'arranged systematically', as it corresponds with the passive construction of the verb.
I file sono messi in ordine alfabetico.
The files are arranged in alphabetical order.
In this sentence, 'messi' is the past participle of the verb 'mettere', agreeing with its plural subject 'i giocatori', and it refers to 'being placed on the field'.