Spanish verbs. Spanish verbs form one of the more complex areas of Spanish grammar. Spanish is a relatively synthetic language with a moderate to high degree of inflection, which shows up mostly in Spanish verb conjugation.
https://en.wikipedia.org/wiki/Spanish_verbs
The perfect tenses [tiempos perfectos] are compound tenses [tiempos compuestos]; that is, they are made up of two parts, a helping verb [verbo auxiliar] and a past participle [participio pasado], for example: he hablado (I have spoken), habías hablado (you had spoken), habremos hablado (we will have spoken).
http://users.ipfw.edu/jehle/courses/perfect1.htm
Haber is the most common of the auxiliary verbs in Spanish as it is used to form the perfect tenses. It is the equivalent of the English have as an auxiliary verb — but it shouldn't be confused when using have meaning possess, which is usually tener. Haber is irregular in most tenses and in the subjunctive mood. It is not used in the imperative mood. It also is seldom used on its own in compound tenses, although it is used to form the compound tenses of other verbs. Irregular forms are shown below in boldface.
https://www.thoughtco.com/conjugation-of-haber-3079627
Exceptions in the perfect participle. 1  If there is a vowel before the ido-ending, we have to add an accent on the i of the ending. This shows us that each vowel is pronounced separately (not a diphthong). 2  Some verbs have an irregular and/or regular participle form. These can be found in the following list:
https://espanol.lingolia.com/en/grammar/tenses/preterito-pluscuamperfecto
An inflected form of the auxiliary verb haber. In case of the Pretérito Pluscuamperfecto de Subjuntivo A tense, we use the Pretérito Imperfecto de Subjuntivo A (Imperfect Subjunctive A) conjugation of haber. Past Participle, which is always the same in every compound tense for a given verb.
http://www.howtoconjugatespanishverbs.com/learn-hacer-conjugation-in-preterito-pluscuamperfecto-a-subjuntivo/
(main verb: written ; auxiliary verb: had) We had been stranded for six days. (main verb: been ; auxiliary verb: had) In Spanish, the past perfect tense is formed by using the imperfect tense of the auxiliary verb “haber” with the past participle. You have already learned in a previous lesson that the past participle is formed by dropping the infinitive ending and adding either -ado or -ido.
http://studyspanish.com/verbs/lessons/pastperfect.htm/
Pretérito Pluscuamperfecto. Introduction. We use the pretérito pluscuamperfecto (past perfect) to describe actions that took place before a certain point in the past. We always use the past perfect when we are telling a story (in the simple past) and then want to look back at something that happened earlier.
https://espanol.lingolia.com/en/grammar/tenses/preterito-pluscuamperfecto
Notes: There are 2 different forms of the verb haber. The table below shows the conjugation of haber when used as an auxiliary verb or helping verb - for example: haber estudiado (to have studied) The verb haber can also mean to be - for example: - there is, there are, there was, there have been, etc. The conjugation table for the impersonal form of haber is found here Haber (impersonal)
https://www.123teachme.com/spanish_verb_conjugation/haber
The past perfect tense [el pluscuamperfecto]: To form the past perfect, use the imperfect of haber plus the masculine singular form of the past participle: había hablado. I had spoken. habías hablado. you had spoken.
http://users.ipfw.edu/jehle/courses/perfect1.htm
Learn hacer conjugation in Pretérito Pluscuamperfecto A. hacer means: to do, to make. Click to see all conjugation charts of hacer in every tense. In this conjugation lesson we will see how to inflect the verb hacer in the Pretérito Pluscuamperfecto A tense of the Subjuntivo mood.
http://www.howtoconjugatespanishverbs.com/learn-hacer-conjugation-in-preterito-pluscuamperfecto-a-subjuntivo/
what is the form of haber in the preterite pluscuamperfecto
The form of haber in the preterite pluscuamperfecto is conjugation of haber.