h₁enter
“between, among, within”between
PIE preposition meaning between, among, or within. Source of Latin inter, English "enter," and related spatial terms.
Discussion
*h₁enter is a Proto-Indo-European preposition meaning "between," "among," or "within," one of the most productive spatial morphemes across daughter languages.
Latin inter "between, among" is the primary reflex, yielding a vast English vocabulary: interest, internal, international, internet, intercept, interfere, interpret, interval, and many more. The prefix inter- remains fully productive in English word formation.
Sanskrit antár "within, between" and Avestan antar- confirm the Indo-Iranian branch. Old Irish eter "between" continues the Celtic form. The initial laryngeal *h₁ is reflected in the e-vocalism.
In Germanic, the root appears in Old English in "in" and inn "within" (though these are more commonly derived from *h₁en). German unter/inter- (borrowed from Latin) and English enter (via Old French entrer, from Latin intrāre) bring the root back into Germanic through Romance channels.
The semantic core is interiority and betweenness—being situated among or inside a group or space. Modern descendants include English enter, interior, internal, inter- (prefix), and the learned Latin borrowings: interest, international, internet, interval, intercept, and interpret.
Notes
Source of Latin "inter" (between), English "enter". Interior spatial relation.