Augment (Indo-European)
The augment is a prefix used in certain Indo-European languages (Indo-Iranian, Greek, Armenian and Phrygian) to indicate past time. The augment is of rather late origin in Proto-Indo-European, and in the oldest daughter languages such as Vedic Sanskrit and early Greek, it is used optionally. The same verb forms when used without the augment carry an injunctive sense. The augment originally appears to have been a separate word, with the potential meaning of 'there, then', which in time got fused to the verb. The augment is "" in PIE ("é-" in Greek, "á-" in  Sanskrit) and always bears the accent. Greek. The predominant scholarly view on the prehistory of the augment is that it was originally a separate particle, although dissenting opinions have occasionally been voiced. Homeric Greek. In Homer, past-tense (aorist or imperfect) verbs appeared both with and without an augment. Ancient Greek. In Ancient Greek, the verb λέγω "légo" "I say" has the aorist ἔλεξα "élexa" "I said." The initial ε "e" is the augment. When it comes before a consonant, it is called the "syllabic augment" because it adds a syllable. Sometimes the syllabic augment appears before a vowel because  the initial consonant of the verbal root (usually digamma) was lost: When the augment is added before a vowel, the augment and the vowel are contracted and the vowel becomes long: ἀκούω "akoúō" "I hear", ἤκουσα "ḗkousa" "I heard". It is sometimes called the "temporal augment" because it increases the time needed to pronounce the vowel. Modern Greek. Unaccented syllabic augment disappeared during the Byzantine period as a result of the loss of unstressed initial syllables. However, accented syllabic augments have remained in place. So Ancient ἔλυσα, ἐλύσαμεν ("élūsa", "elū́samen") "I loosened, we loosened" corresponds to Modern έλυσα, λύσαμε ("élisa , lísame"). The temporal augment has not survived in the vernacular, which leaves the initial vowel unaltered: Ancient ἀγαπῶ, ἠγάπησα ("agapô", "ēgápēsa") "I love, I loved"; Modern αγαπώ, αγάπησα ("agapó", "agápisa"). Sanskrit. The augment is used in Sanskrit to form the imperfect, aorist, pluperfect and conditional. When the verb has a prefix, the augment always sits between the prefix and the root. The following examples of verb forms in the third-person singular illustrate the phenomenon: When the root starts with any of the vowels "i-", "u-" or "ṛ", the vowel is subject not to guṇa but vṛddhi. Constructed languages. In  J. R. R. Tolkien's Quenya, the repetition of the first vowel before the perfect (for instance "utúlië", perfect tense of "túlë", "come") is reminiscent of the Indo-European augment in both form and function, and is referred to by the same name in Tolkien's grammar of the language.