kell + Infinitive

The pattern kell + infinitive is essential for daily life. Here is how it works:

1. General Necessity
To express that something 'must be done' in general, use kell + the plain infinitive. Note that the word kell itself stays frozen in the third-person singular and never changes for person in this structure (forms like kellek or kellesz are not used here).
Example: Sokat kell aludni. (One must sleep a lot.)

2. Specific Necessity (Personal)
When a specific person has the obligation, standard Hungarian uses the personal infinitive. To form this, you take the infinitive, drop the entire -ni marker, and add personal endings. These endings follow vowel harmony:
• -nom / -nem / -nöm (I)
• -nod / -ned / -nöd (You)
• -nia / -nie (He/She/It)
• -nunk / -nünk (We)
• -notok / -netek / -nötök (You plural)
• -niuk / -niük (They)
Example: látni (to see) drops the -ni to become lát-, then adds -nom → Látnom kell. (I must see.) Similarly, menni (to go) drops the -ni to become men-, making it men- + -nem = mennem → Mennem kell. (I must go.)

3. The Subject (Dative Case)
The person who has the obligation is in the dative case (-nak/-nek). When using the personal infinitive, a dative pronoun (like nekem) is typically omitted, as the ending already shows the person. However, in everyday colloquial Hungarian, it is very common to simply use the plain infinitive with a dative subject instead (e.g., Nekem el kell menni. instead of El kell mennem.). Note that prescriptive Hungarian grammar considers this incorrect, so you should use the personal infinitive in formal writing or language exams. Nouns in the dative case are usually kept for clarity in both structures.
Example: Péternek kell mennie. or colloquially Péternek kell menni. (Péter must go.)

4. Word Order with Prefixes
If the verb has a verbal prefix, the word kell usually splits the prefix from the verb in neutral sentences (prefix climbing). However, in negative sentences and sentences with question words, the prefix stays attached to the verb. This happens because the negator nem or the question word takes the focus position right in front of kell, blocking the prefix from moving there.
• Neutral: El kell mennem. (I must leave.)
• Negative: Nem kell elmennem. (I don't have to leave.)
• Question: Mikor kell elmennem? (When must I leave?)

5. Tense and Mood
You can change the tense or mood of the obligation by changing kell or adding a time word:
• Past: kellett (had to) — Várnom kellett. (I had to wait.)
• Future: kell majd (will have to) — El kell majd mennem. (I will have to leave.)
• Conditional: kellene or the common spoken short form kéne (should) — Aludnod kellene. / Aludnod kéne. (You should sleep.)

6. The "Must Not" Trap
Because kell translates to "must", English speakers naturally assume that nem kell means "must not". However, nem kell means a lack of obligation ("don't have to" or "need not"). To express a negative obligation ("must not"), Hungarian uses entirely different words: nem szabad or tilos.
Example: Nem kell mennem. (I don't have to go.) vs. Nem szabad mennem. (I must not go.)