Questions & Answers about Vatra se širi područjem.
Se is the clitic used with many Croatian verbs that are reflexive or middle-voice in meaning. Here, širiti se means to spread.
So:
- širiti = to spread something, to expand something
- širiti se = to spread, to expand, to extend on its own
In this sentence, the fire is not spreading something else; the fire itself is spreading, so Croatian uses širiti se.
Compare:
- Vatrogasci šire crijevo. = The firefighters are extending/spreading the hose.
- Vatra se širi. = The fire is spreading.
Širi is the 3rd person singular present tense form of širiti se.
It matches vatra, which is singular:
- ja se širim = I spread
- ti se širiš = you spread
- on / ona / ono se širi = he / she / it spreads
Since vatra is grammatically singular, the verb is širi.