This is the 178th most frequent Swedish word.
enda
"Enda" means "only" or "sole" in English.
Here, 'enda' is used as an adjective meaning 'only/single/unique' to specify that the speaker is the sole person who knows the secret.
Jag är den enda som känner till hemligheten.
I am the only one who knows the secret.
In this sentence, 'enda' is used to emphasize that a singular example exists.
Det är otroligt att detta är det enda exemplet vi har.
It's incredible that this is the only example we have.
Here, 'enda' reinforces the meaning of 'ett ord' to denote a complete lack of any words being written, intensifying the exclusivity of 'single' as in 'not even one.'