The particles of the Proto-Indo-European language (PIE) have been reconstructed by modern linguists based on similarities found across all Indo-European languages. The following article lists and discusses their hypothesized forms.
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, Germanic, Indo-Iranian and Sabellic; Latin and Greek preserve postpositions vestigially.
Reflexes, or descendants of the PIE reconstructed forms in its daughter languages, include the following.
Luw. anda, Carian nt_a, Goth. in, ON í, Ir. in/i, Lith. į, Ltv. iekšā
Av. aipi, Lith. api-, apie, Alb. afër "near"
Pers. ?/zēr, ON und, Goth. undar, Gm. untar/unter, Arm. ĕndhup/ĕnthub