1. Formally, Present Stems have a Reduplication either Full (sometimes maintained throughout the conjugation) or Simple, which normally consists of the initial consonant of the root followed by -i-.
In the Meaning, Reduplication can have an especial value (of iteration or intensity) or simply an opposed value; in every case, thus, it distinguishes the verb in its different forms.
2. The Form of Reduplication:
I. Full Reduplication, normally of the Present Stem, repeats the Root or at least the group consonant/sonorant+vowel+consonant/sonorant: galgal, talk, bherbher, endure, mormor, whisper, etc.
Full reduplication is also that which repeats a Root with vowel+consonant/sonorant; as, ulul, cry aloud.
II. Simple Reduplication is made:
a. With consonant + i. In athematic verbs; as, si-sde (sit down, settle, from zero-grade root sed, sit); in thematic verbs; as gi-gno, bhi-bher, etc.
NOTE. Reduplication is, as already stated, optional in IE III: gignosko/gnosko, dido/do, bibo/poi, etc.
There are some intensives half full, half simple reduplicated stems, as in dei-dik, teach. There are other forms with -w, -u, as in leu-luk, shine. There are also some perfects.
b. With consonant + e/e. ai. dedhe, dedo.
Simple Reduplication in e is given mainly in the Perfect, while that in i is characteristic of the Present. Reduplication in e is also often found in intensives in Southern Dialects.
NOTE. As a matter of fact, reduplication doesn't affect the vowel in inflection: bibherti / bibhrmes, istami / istames.
3. The Meaning of Reduplicated stems: It is mainly a southern feature (Indo-Iranian and Greek) the systematic opposition Basic Verb / Deverbative Reduplicated to obtain an Iterative-Intensive. There is another meaning, that of the Desideratives, which are reduplicated with -i- + Root + -se/o, e.g. meno /mimnso, think, the Reduplicates here are called Terminatives.
NOTE. Although the Iterative-Intensives, Desideratives and sometimes Terminatives were not generally extended to the Northern Dialects, we consider it an old resource of the IE II, older than that of the opposition Present-Perfect. We therefore include this dialectal feature in the global system as a possibility with already known vocabulary, although not as a general way to create new words from Basic Verbs.