In English, the pluperfect is expressed by using the auxiliary verb "had" followed by the past participle: "She had studied."
In Spanish, the pluperfect is formed in the indicative mood by using the imperfect form of haber (había, habías, había, habíamos, habíais, habían) followed by the past participle: Había estudiado.
In Spanish, the pluperfect can also be used in the subjunctive mood by preceding the past participle with the imperfect subjunctive of haber (hubiera, hubieras, etc.): Dudo que hubiera estudiado (I doubt she had studied).
The pluperfect usages of the two languages are almost identical, so it is usually safe to translate the pluperfect of one language into the pluperfect of the other. However, in some contexts, especially in colloquial usage, the simple past tense can be substituted for the pluperfect in either language.

