This is the 824th most frequent Czech word.
hlavu
The Czech word "hlavu" means "head" (accusative singular form).
In this sentence, 'hlava' is in the nominative case and refers directly to the physical head of a person.
Bolí mě hlava, asi mám migrénu.
My head hurts, I probably have a migraine.
This expression uses 'hlavu' metaphorically to mean staying calm and composed in stressful situations, and it is in the accusative case as the direct object of the verb 'ztrácej.'
Neztrácej hlavu, každý problém má řešení.
Don't lose your head; every problem has a solution.
Here, 'hlavu' is used as a direct object in the accusative case, referring to the person's head metaphorically to imply calming down.