The Key to the Perfect Tenses
In order to understand the compound, or perfect tenses, it is useful to go back to some basics. Let's start with the global name of this group of tenses formed by the conjugation of haber in all the simple (or one-word) tenses (including the two simple tenses of the subjunctive mood). The term compound tense refers to the fact that a particular tense is not a one-word tense, like the present indicative.
When the term perfect tense is used, it refers to the radical, or root meaning of the word perfect. It is derived from the Latin prefix per which means completely or thoroughly and fectum, a participial form in Latin that corresponds to hecho in Spanish and done or made in English. Thus, as a grammatical term, perfect means completely done, or performed. In that sense, it shares a lot with the tense that in Spanish is called the preterite (which is a direct derivative of the perfect tense in Latin), but it has acquired a special meaning and now refers only to the tenses that are formed with the tenses of haber plus a past participle.
The past participle of a verb, when used with the tenses of the auxiliary verb haber, is invariable. It will be used with all the persons and numbers of all the various forms of the perfect tenses, seven in all (two of which are subjunctives). The only thing that changes — is conjugated — is the verb haber. Here is an overview of the compound tenses and a list of the irregular past participles.
How do the simple tenses of a given verb relate to its compound tenses? To illustrate this, let's do a quick synopsis of an easy verb: comer. Let's use the tú form.
Note that comes means you eat. The simple verb is conjugated to agree with the subject — tú. In order to form the present perfect tense, which means you have eaten, you must conjugate the verb haber, not comer, in the simple present tense, to agree with the subject: has. Next, the verb comer is put (not conjugated) in its participial form: comido, thus we have: has comido. What this tells us is that the present perfect of any verb is based on the simple present of haber compounded with the past participle of that verb.
The past perfect, or pluperfect, likewise is formed by conjugating the verb haber in the imperfect (habías — to continue using the tú form as a model): habías comido, which means you had eaten. In Spanish, the preterite anterior, using the preterite of haber plus the past participle, is not used much in speech — and it means the same thing as the perfect tense using the imperfect of haber: hubiste comido = you had eaten.
The other perfect tenses also maintain this same relationship with their corresponding simple tenses. Thus, the simple conditional, you would eat (comerías) is related to the conditional perfect, habrías comido (you would have eaten). Likewise, the simple future, you will eat, corresponds to the future perfect, you will have eaten.
Now we arrive at the two perfect tenses of the subjunctive mood: the present perfect subjunctive and the pluperfect subjunctive. As tenses, they are the same as the present perfect and the pluperfect, respectively. In fact, when translated into English, they come out the same: Juan ha comido and Dudo que Juan haya comido. John has eaten and I doubt that John has eaten. Thus, all forms of the present of haber, indicative and subjunctive, will translate into English as either has or have. In like manner, all forms of the pluperfect indicative and the pluperfect subjunctive render the verb haber in English as had: Sabía que Juan había comido and Dudaba que Juan hubiera comido. I knew John had eaten and I doubted that John had eaten.