Learn Italian: Il corriere è cordiale con tutti i clienti. - The courier is cordial with all the customers.

In Italian, when tutto (all) modifies a noun, it must be followed by the definite article. Even when English simply says "all customers", Italian requires "all the customers", making it tutti i clienti.

Is cliente always a masculine noun?

No, cliente is a noun that ends in -e, meaning it can be masculine (il cliente) or feminine (la cliente) depending on the person. The masculine plural i clienti used here covers either an all-male group or a mixed group.

Why doesn't the adjective cordiale end in -o to match the masculine noun il corriere?

Cordiale belongs to a specific group of adjectives that always end in -e in the singular. These adjectives don't change for gender, so they look exactly the same whether they describe masculine or feminine nouns. In the plural, they always change to -i.

Is corriere related to the English word "career"?

It looks similar, but it's a false friend! Il corriere means "the courier" or "the delivery person" (you'll also see it in famous newspaper titles like Il Corriere della Sera). If you want to talk about your professional "career", the Italian word is la carriera.