Learn Italian: Ho due braccia e dieci dita. - I have two arms and ten fingers.

In Italian, a small group of nouns (many of them body parts) are masculine in the singular but become feminine and end in -a in the plural. This is a leftover from Latin. So instead of regular plural endings, we get these special -a endings.

What are the singular forms of these two words?

The singular of braccia (arms) is il braccio (the arm). The singular of dita (fingers) is il dito (the finger). Notice how they are perfectly regular masculine words when there is only one!

If I want to say "the arms" or "the fingers", which word for "the" do I use?

Because these irregular plurals become feminine, you must use the feminine plural article le. You would say le braccia (the arms) and le dita (the fingers). Any adjectives describing them must also be feminine plural.

Does dita only mean "fingers"? What about toes?

In Italian, dita covers both "fingers" and "toes"! If you need to be specific to avoid confusion, you can say le dita delle mani (the fingers of the hands) or le dita dei piedi (the toes, literally the fingers of the feet).