KELL = HAVE TO, MUST, NEED TO
If it takes the infinitive form, then it is a general reference to someone, something. If it takes the infinitive with personal suffixes, it specifically refers to someone, something. Anyway, it expresses obligation.
Formation: This verb may require the dative pronouns, but it is not mandatory. It takes the main verb in its infinitive form either with personal suffixes or not:
NEKEM + KELL + INFINITIVE VERB
Present: kell Past: kellett Future: kell majd
Ennyi munka után enni kell.
After so much work one has to eat.
Ennyi munka után enned kell.
After so much work you have to eat.
Ennyi munka után enni kellett.
After so much work one had to eat.
Ennyi munka után enned kellett.
After so much work you had to eat.
Ennyi munka után enni kell majd.
After so much work one will have to eat.
Ennyi munka után enned kell majd.
After so much work you will have to eat.
See the difference? If there’s a simple infinitive of the main verb, it refers to something generally. With an infinitive conjugated, it refers to something/somebody specifically. I know I keep saying the same, but I think it is important.
Look at the diversity of the English use when it comes to obligation:
Tudnom kell. – I need to know.
Mennem kell. – I must go.
Enned kell valamit. – You should eat something.
Korán kell kelnünk, hogy el ne késsünk.
We have to get up early so that we’re not late.
NOTE! It’s important that you don’t conjugate kell like in English. You conjugate the infinitive of the main verb and leave kell as it is.
If you talk about a specific person or thing, you have to use the suffixes -nak, -nek! Example:
A barátomnak tízkor meg kell érkeznie.
My friend should arrive at ten.
Ahogy látom, a kutyának sürgősen orvoshoz kell mennie.
As I see, the dog must go to a doctor urgently.
I didn’t mention the conditional form of kell because it is translated with should in English. More about that next time.