How do you write, "prepared by" in Latin?

Answer 1

"prepared" = paratus/a/um + many other endings depending on who or what is prepared, so you cannot single out any one particular ending in a short phrase like your "prepared by" ;

"by" = a/ab + ablative (when the word after "by" refers to a person, Ex. 1, 2,) the ablative alone (when the word after "by" is not a person, Ex. 3).

1. the food prepared by many cooks (was enjoyed by all) = cibus a multis coquis paratus ;

2. the plan prepared by the general (encouraged the soldiers) = consilium ab imperatore paratum ;

3. bread prepared by hand = panis manu paratus .

As the previous answerers have stated, context determines the ending according to who/what is prepared.

"Paratus" must be used as an adjective, however (e.g., the gladiator, extremely well prepared/paratus for his next fight, made short work of his opponent), and not as a verb (the meal is being prepared by Mary, cena a Maria paratur.)

Answer 2

we need the context, sweetie: the meal was prepared by? the student was prepared by? .....

Answer 3

abparatus ( male )
abparata (female)
abparatum (neuter)