Learn French: C'était une urgence grave, alors nous avons appelé une ambulance. - It was a serious emergency, so we called an ambulance.

This sentence shows a classic mix of past tenses! C'était describes the background situation or state of things ("it was an emergency"). Nous avons appelé is the specific action you took because of that situation ("we called"). You use the imparfait to set the scene, and the passé composé for the events that actually happened.

Why do we say C''était instead of Il était to mean "It was"?

In French, when "it is" or "it was" is followed by a noun (like une urgence), you must use c'est (or in the past, c'était). You would usually only use il était if it were followed by an adjective alone, for example: il était grave (it was serious).

Why does the adjective grave come after urgence?

Most French adjectives go after the noun they describe. Only a specific group of common, short adjectives—usually describing Beauty, Age, Goodness, or Size (often remembered as "BAGS")—go before the noun. Grave (serious) doesn't fit into those categories, so it follows the normal rule and goes after the noun.

Why isn't there an "s" at the end of appelé since the subject is nous (we)?