Learn Italian: Lo studente mostrava un buon impegno. - The student showed a good effort.

The adjective buono changes its ending when it comes directly before a noun, following the exact same rules as the indefinite articles like un or uno. Because impegno is a masculine word starting with a vowel, it would take the article un, so buono drops its final letter and shortens to buon.

Why does the sentence start with Lo studente instead of Il studente?

In Italian, masculine singular nouns that start with an s followed by another consonant (like the st in studente) require the definite article lo instead of the usual il.

Why is the verb mostrava used here instead of the past tense ha mostrato?

The verb mostrava is in the imperfect tense, which we use to describe an ongoing, habitual, or continuous state in the past. It suggests the student was consistently showing a good effort over a period of time, rather than just showing it once as a single, completed event.

I have seen impegno translated as "appointment" before. How does it mean "effort" here?

The word impegno is very versatile. While it often means a commitment or prior engagement (like a personal appointment you cannot miss), in the context of school, studying, or work, it translates to "effort", "dedication", or "commitment" to a task.