Vowel-Shortening Stems

Hungarian has a group of approximately 60–80 nouns and a few adjectives where the long vowel in the final syllable of the stem shortens when specific suffixes are attached. This is not a general rule of the language, but a characteristic of these specific ancient roots.

1. The Vowel Changes:
The most common shifts are:

• á → a (e.g., nyár → nyarat)
• é → e (e.g., kéz → kezet)
• í → i (e.g., víz → vizet)
• ó → o (e.g., ló → lovat - note: this is a v-inserting stem)
• ó → a (e.g., tó → tavat, hó → havat, szó → szavak - note: these are also v-inserting stems. Exception: Unlike tó and hó, szó does not shorten or insert a 'v' in the accusative, remaining szót.)
• ő → ö (e.g., kő → követ - note: this shift is exclusive to v-inserting stems like kő, cső, tő)
• ú → u (e.g., út → utat)
• ű → ü (e.g., tűz → tüzet)

2. Triggering Suffixes:
Shortening occurs when certain suffixes requiring a linking vowel are attached. These include:

• Plural -k (vizek)
• Accusative -t (vizet)
• Possessive suffixes like -m, -d, -unk/-ünk, as well as the 3rd person -a/-e and -uk/-ük (kezem, utunk, keze, vize). Exception: Stems ending in -t or -d with a long high vowel (like út, kút, híd) take -ja/-je and do not shorten in the 3rd person possessive (útja, hídja).
• Adjective-forming suffixes like -s (vizes, utas)
• The comparative suffix -bb for adjectives (nehezebb)
• Verb-forming suffixes like -z and -l (kéz → kezel, út → utazik, nyár → nyaral)

3. Non-Triggering Suffixes & The Superessive Exception:
Suffixes that do not use a linking vowel (mostly case endings) do not cause shortening. The stem remains long:

• vízben (in water)
• kéznél (at the hand)
• útig (until the road)

Crucial Exception: The superessive case suffix -n (on) requires a linking vowel but does not trigger shortening for most of these stems, and it takes standard mid vowels (-o/-e/-ö) instead of low vowels (e.g., nyáron, úton, vízen, kézen, tűzön). The only exceptions to this exception are the v-inserting stems, which do shorten (e.g., lovon, kövön).

4. Important Notes:
When shortening occurs, these stems act as 'lowering stems,' meaning they take the low linking vowels -a/-e instead of the standard -o/-e/-ö (except for the superessive case mentioned above). Additionally, a small number of common adjectives follow this exact pattern, such as nehéz (heavy/difficult) → nehezet, elég (enough) → eleget, and kevés (few/little) → keveset / kevesebb.

5. Modern Usage and Compounds:
Compound words inherit the shortening behavior of their root (e.g., ásványvíz → ásványvizet, főút → főutat). Furthermore, modern Hungarian is slowly losing the shortening for some words, and both forms are accepted in contemporary dictionaries (e.g., fonalat / fonálat, sugarat / sugárat).