Hi all,
My Latin teacher suddenly sprung this on us, and there’s a test on it tomorrow. Can anybody explain this to me? I understand how to use it as a verb form, but I’m lost as to how it’s used as an adjective. As in…the abandoned house. (Relictum is the 4th principle part…so is it relicta casa?)
Thank you so much for your help 
The perfect passive participle is basically an adjective, like all the other participles. Because it’s an adjective, it must agree with its noun in case, number, and gender.
As the name suggests, you need to attend to its tense and voice to make sense of it. Take the verb “to abandon”: relinquo, relinquere, reliqui, relictus. The fourth principal part is always the perfect passive participle.
Since the participle is perfect, this action happened in the past (specifically, prior to the action of the main verb). Since it is also passive, the action happened to whatever noun it is modifying.
abandoned house = domus relicta (notice that relicta agrees in gender with domus, a feminine noun despite the fact it’s second declension)
The abandoning of the house is a completed action in the past. It has already been abandoned. This is the meaning of “perfect.”
The house didn’t abandon anyone else; rather, it received this action. This is the meaning of “passive.”
Many past participles in English are formed by adding “-ed” to the word. E.g., abandon → abandoned. However, there are also lots of irregular past participles, so you might need to pause and remember the form. E.g. sing–>sung. drink–>drunk. speak–>spoken, etc.