A special Past or Preterite is that of the European dialects (i.e., the Northern and Greek), sometimes called Future Past, which is formed by two elements: a verbal stem followed by a vowel (-e, -a, -i, -o) and an auxiliary verb, with the meanings to be (es), to become (bheu) or to make (dhe, do).
NOTE. Although each language has its own formations, they have a common origin, probably unstable at first.
The Compound Past is comprised of three parts: the forms of the first and second elements and the sense of the compounds.
1. The First Element can be
a. A Pure Root
b. A Pure Stem, with the same lengthening as the rest of the verb.
c. A Pure Stem lengthened but alternating with the Present: normally Present Ø / Past with full vowel.
d. A Pure lengthened Stem, opposed to a thematic Present (and Imperfect).
NOTE. Originally, then, the Compound Pasts are derived from a root or a stem with vowel ending; wether that of the verb or that of the Past. They are, then, Pasts similar to the others, but, instead of receiving endings, they receive a second stem.
2. The second element is an auxiliary verb; dhe in gr. and ger., bheu in lat. and cel. and do- in bsl.
3. They are, as said, Pasts as the others we have seen, and they could function differently according to the needs of the languages.
NOTE. These forms have not been systematized, as there is no unity, and no especial needs have been still found for them to be revived. We present this possibility, though, for any possible future use, to show that this formations (although not unitary) have the same pattern shared by the Northern Dialects.