Learn Italian: Bisogna comprare il compensato, ovvero il materiale per il progetto. - One must buy the plywood, namely the material for the project.

In this sentence, ovvero acts as an explanatory marker meaning "namely" or "that is to say". It introduces a clarification, explaining that the plywood is the specific material needed for the project. While ovvero can sometimes be used as a formal word for "or" (like o), here its job is to rephrase and define what came before.

Is the comma before ovvero important here?

Yes, when using ovvero as an explanatory marker to mean "namely", you should place a comma before it. The comma signals a pause before you clarify the previous term, which in this case is il compensato. If ovvero were used simply to mean "or" between two distinct alternative choices, the comma would usually be dropped.

Why use Bisogna comprare instead of Dobbiamo comprare?

Bisogna followed by an infinitive like comprare expresses a general necessity, translating to "it is necessary to buy" or "one must buy". It is strictly impersonal and never takes a specific subject like "I" or "we". You would use Dobbiamo comprare if you specifically meant "we must buy", but Bisogna comprare keeps the statement broad and general.

Why is the definite article il used before compensato if the English translation just says "plywood"?