Noun structures are made up of minimal units of meaning. Added to roots, suffixes and endings add units of grammatical meaning. These morphemes (roots, suffixes, and endings) make up the morphology of older Indo-European words. Case, number, and gender or noun class endings are added to create nouns.

Endings are added directly to the root of nouns called "root nouns", nouns which belong to the oldest layer of Indo-European. Also old are neuter nouns formed by adding with the heteroclitic (alternating) suffix, -r/-n- (--r for the nominative and accusative cases with no ending and -n- before the endings of other the cases. Other old noun classes, named after the vowel suffix, were formed by adding stem vowels either as the nominative (and accusative neuter) ending and before other case endings. The youngest Proto-Indo-European noun class was the -o-stem noun class.

Derived nouns included infinitives, agent, and instrument nouns derived from verbal roots or stems.