This is the 549th most frequent Portuguese word.
medo
Fear; an unpleasant emotion caused by the perception of danger or threat.
The word 'medo' is used here to express the feeling of fear, followed by 'de' to indicate what is feared.
Eu tenho medo de escuro.
I am afraid of the dark.
In this sentence, 'medo' is a noun referring to the general concept of fear.
O medo pode ser superado com coragem.
Fear can be overcome with courage.
'Medo' here signifies a specific fear inhibiting someone, directly linked to the preposition 'de' to describe its cause.