Refers to a large-scale fire, often one that causes significant damage. Commonly used in news reports.
Last night, a large fire broke out in this district.
There was a large fire in the city center last night.
大火のため、多くの家が焼けた。
Many houses burned down due to the conflagration.
During the Edo period, this town was struck by large fires many times.
Many houses were destroyed by the large fire.
火災 is the formal, official term for a fire disaster, whereas 大火 is the common term used in news and everyday speech for a big fire.
大火事 is a more colloquial way of saying the same thing as 大火, which sounds slightly more formal and is favored in written/news contexts.
大火 is a large, devastating fire, the opposite in scale of a 小火, which stays small and is quickly extinguished.
Compound of 大 (large) and 火 (fire). The reading たいか is the on'yomi of both characters.