This is the 1654th most frequent Polish word.
ostatnia
"Last" or "final."
'Ostatnia' in this sentence is an adjective describing 'szansa' (chance), indicating that it is the final one available.
To jest moja ostatnia szansa.
This is my last chance.
Here, 'ostatnia' qualifies 'książka' (book), referring to the most recent or final one in a given context.
Ostatnia książka była bardzo ciekawa.
The last book was very interesting.
'Ostatnia' describes 'osoba' (person), indicating it is the final one, possibly in a sequence or metaphorical sense.