Demonstrative Assimilation

When using demonstrative pronouns to point out specific entities, Hungarian grammar strictly requires the demonstrative to agree with the noun in both case and number. Furthermore, when modifying a noun (attributive use), the demonstrative must always be followed by the definite article (a/az). When used as an independent pronoun (e.g., Ezt akarom), no article is needed.

The Assimilation and Elision Rules:
When attaching most oblique case suffixes that begin with a consonant to the singular demonstratives ez and az, the final z undergoes complete regressive assimilation to the initial consonant, creating a double consonant:

• ez + ben = ebben (in this)
• az + ra = arra (onto that)

For consonant-initial postpositions modifying a noun, the final z is traditionally dropped (elided), and the demonstrative and postposition are written as separate words. The postposition must also be repeated after the noun:

• e mellett az épület mellett (beside this building)

Note: In modern colloquial Hungarian, retaining the z (e.g., ez mellett az épület mellett) is very common, but prescriptive sources consider this non-standard. It should be avoided in formal writing and on grammar tests. When used as independent pronominal adverbs (not modifying a noun), they are written as one word (e.g., emellett - 'beside this/besides').

For vowel-initial postpositions modifying a noun, the z is kept, and they are written as separate words:

• ez alatt a híd alatt (under this bridge)
• az előtt a ház előtt (before that house)

Important Exceptions and Irregularities:

• Plural demonstratives: The plurals ezek and azok end in k, not z, so they do not undergo assimilation with case suffixes (e.g., ezekben, azokra). Furthermore, when used with postpositions, they remain two separate words (e.g., ezek mellett).
• The accusative case: Although -t is a consonant, the z does not assimilate to it (ezt, azt).
• Vowel-initial suffixes: Suffixes like the superessive -on/-en/-ön do not trigger assimilation (ezen, azon). Similarly, the causal-final case (-ért) simply attaches to form the highly frequent words ezért (for this / therefore) and azért (for that / therefore).
• The terminative case: Even though -ig starts with a vowel, it triggers a highly irregular assimilation to dd (eddig, addig).
• The temporal suffix -kor: This suffix triggers assimilation to form the highly frequent words ekkor (at this time) and akkor (at that time / then).
• The instrumental case and translative -vá/-vé: For the instrumental case, both progressive assimilation (ezzel, azzal) and regressive assimilation (evvel, avval) are perfectly grammatical and standard. However, for the translative case, only progressive assimilation is standard (ezzé, azzá).

Pronunciation Note:
When attaching the allative suffix -hoz/-hez, the resulting forms are ahhoz and ehhez. While orthographically geminated (double h), this is a rare exception to Hungarian consonant lengthening rules. It is pronounced as a single, short /h/ (ahoz, ehez).