Proto-Indo-European particles

The particles of the Proto-Indo-European language (PIE) have been reconstructed by modern linguists based on similarities found across all Indo-European languages.

Adverbs used as adpositions
Many particles could be used both as adverbs and postpositions. This is similar to modern languages; compare English He is above in the attic (adverb) and The bird is above the house (preposition). The postpositions became prepositions in the daughter languages except Anatolian, Indo-Iranian and Sabellic; some of the other branches such as Latin and Greek preserve postpositions vestigially.

Reflexes, or descendants of the PIE reconstructed forms in its daughter languages, include the following.

Untranslated reflexes have the same meaning as the PIE word.

In the following languages, two reflexes separated by a slash mean:
 * English: Old English / Modern English
 * German: Old High German / New High German
 * Irish: Old Irish / Modern Irish
 * Persian: Old Persian / Modern Persian
 * Tocharian: Tocharian A / Tocharian B

Negating prefixes (privatives)
Two privatives can be reconstructed, and, the latter only used for negative commands. The privative prefix is likely the zero grade of.

Adverbs derived from adjectives
Adverbs derived from adjectives (like English bold-ly, beautiful-ly) arguably cannot be classified as particles. In Proto-Indo-European, these are simply case forms of adjectives and thus better classified as nouns. An example is "greatly", a nominative-accusative singular.

Conjunctions
The following conjunctions can be reconstructed:

†Placed after the joined word, as in Latin Senatus populus-que Romanus ("Senate and people of Rome"), -que joining senatus and populus.

Interjections
There is only one PIE interjection that can be securely reconstructed; the second is uncertain.