Learn Finnish: Uutinen jätti meidät kaikki sanattomiksi.

The verb jättää (to leave) requires the translative case (ending in -ksi) when expressing the state or condition someone is left in. Because the news caused us to enter the state of being speechless, the adjective describing that state takes this ending.

Why do we use the plural form sanattomiksi instead of the singular sanattomaksi?

The word describing the resulting state must agree in number with the object it describes. Since the object is the plural meidät kaikki (us all), the adjective must also take the plural translative form, which includes the plural marker -i- right before the -ksi ending.

Why does the object use the form meidät kaikki?

The action of leaving us speechless is a completed result, so the verb jättää takes a total object. For personal pronouns like me (we), the total object is the special accusative form ending in -t, giving us meidät. The word kaikki (all) does not have a separate -t accusative form, so it simply remains kaikki.

How does the word sanattomiksi break down structurally?