This is the 102nd most frequent Czech word.
začátku
"Začátku" means "beginning" or "start" in English.
Here 'Zpočátku' ('at the start') shares a similar root with 'začátku', and it refers to the early phase of an action or state.
Zpočátku se mi práce zdála jednoduchá, ale později se ztížila.
Initially, the work seemed simple to me, but later it became more difficult.
'Začátku' here is part of the phrase 'od začátku', meaning 'from the beginning,' and indicates the starting phase of a process.
Musíme to probrat od začátku.
We need to discuss it from the beginning.
'Začátku' in this sentence refers to the starting point of an event or situation, which is marked by 'Na' (at).