This is the 422nd most frequent Hungarian word.
oka
"Reason" or "cause."
In this sentence, 'oka' is used in the nominative case to denote the reason or cause for the happiness.
Az ő mosolya az oka annak, hogy boldog vagyok.
Her smile is the reason why I am happy.
Here, 'oka' serves to specify the cause of 'misunderstanding,' demonstrating usage in a possessive form.
A probléma az oka a félreértésnek.
The problem is the cause of the misunderstanding.
In this example, 'oka' identifies the cause or motive for 'delay,' and is used in a similar possessive structure.