Tonitrus longus erat, sed fulgur procul supra montes breve visum est.

to be

Breakdown of Tonitrus longus erat, sed fulgur procul supra montes breve visum est.

• sed: but
• longus: long
• mons: the mountain

Questions & Answers about Tonitrus longus erat, sed fulgur procul supra montes breve visum est.

Why is longus used with tonitrus, but breve with fulgur?

Because Latin adjectives must agree with the nouns they describe in gender, number, and case.

• tonitrus is masculine singular nominative, so its adjective is longus
• fulgur is neuter singular nominative, so its adjective is breve

So the difference is not about meaning, but about grammatical agreement.

What case are tonitrus and fulgur?

Both are nominative singular, because each is the subject of its clause:

• Tonitrus longus erat = the thunder was long
• fulgur ... visum est = the lightning was seen / appeared

In Latin, the subject of a finite verb is normally in the nominative.

What kind of noun is tonitrus?

Tonitrus is a 4th-declension masculine noun meaning thunder.

A learner may expect a noun ending in -us to be 2nd declension, but tonitrus is not. Its genitive is tonitrūs.

So in this sentence:

• tonitrus = nominative singular
• longus agrees with it