Learn Spanish (Latin America): Mi dedo está sucio.

In Spanish, we use está (from the verb estar) to talk about states or temporary conditions. Because being dirty is a state that can change (you can wash it!), we use está. If we used es (from ser), it would sound like being permanently dirty is a built-in characteristic of the finger.

I learned that Spanish uses el or la for body parts instead of "my". Why do we use mi in this sentence?

Great catch! Spanish often uses el or la (the) instead of possessives when an action happens to a body part, or with verbs like doler (to hurt) from this lesson. For example, you would say Me duele el dedo (My finger hurts) using el. But when you are simply describing a body part's condition with estar, using the possessive mi (my) is perfectly normal.

Why does sucio end in an "o"?

Sucio (dirty) is an adjective describing dedo (finger). Because dedo is a masculine singular noun, the adjective must match its gender and number, ending in -o. If you were describing a feminine body part, like your hand (mano), it would change to match: Mi mano está sucia.

Can dedo mean "toe" as well as "finger"?