In the Proto-Indo-European language, the nasal infix is one of several means to form the athematic present tense. It is inserted immediately before the last consonant of the zero-grade root. The infix appeared as in the forms where a full-grade stem would be expected, and as in forms where zero-grade would be expected. For example, the PIE root "to win" would yield a nasal-infixed present stem. These presents are called nasal infix presents or simplynasal presents and are typically activetransitive verbs, often with durative aspect.
Origins
Since the linguistic ancestor of PIE is not known, there can only be speculations about the origins of the nasal infix. It has been suggested that it arose from a suffix which underwent metathesis.
Other present tense markers
Besides the nasal infix, PIE employs a number of affixes to mark the present:,,,,, and others. All in all, PIE has at least 18 ways to form the present tense. For many verbs, several of these presents can be reconstructed simultaneously. For example, Scottish Gaelic loisg "to burn" goes back to, a present of the root which is also the source of Ancient Greek λάμπειν "to shine" via its nasal present. It is not clear why there were so many different types of present forms with no or little discernible differences in meaning. The authors of the Lexikon der indogermanischen Verben proposed that they were derived from a number of prior grammatical aspects with distinct meanings.
Indo-European languages
The effects of the nasal infix can be seen in Indo-European languages like Latin, Lithuanian, Ancient Greek, Sanskrit and Slavic languages. In Latin, Ancient Greek and other daughter languages, the was assimilated to m before labial consonants, and to ŋ, spelled n in Latin and γ in Ancient Greek, before velar consonants. Latin rūpit "has broken" / rumpit "breaks", from, is an example of the first case.
Greek
Greek has some verbs that show a nasal infix in the present as opposed to other forms of the verb:
English and the other Germanic languages show only vestiges of the nasal infix. The only certain remaining example is English stand, with the past tensestood lacking the n. However, it can still be seen in some pairs of Latin loanwords:
Only vestiges are left, like Russianлечь : лягу , сесть : сяду .
Examples
This table shows some examples of PIE root aorists, their infixed present forms and the reflexes in an attesteddaughter language. †The Latin reflexes of the PIE aorist came to be used as the perfect. ‡It is uncertain whether had a nasal infix already in PIE, since Greek λαμβάνω is only attested after Homer.
In J. R. R. Tolkien's constructed language Quenya, the nasal infix forms the past tense of verbs ending in any consonant besides -m, -n, or -r. Thus, cen- "to see" has the past tense cen-në, but mat- "to eat" has not *mat-në but the metathesisedma⟨n⟩t-ë.