Too is a small word that carries a lot of meaning in English. It means “also” or “as well,” adding something to what's already been said. If your friend says, “I love pizza,” and you reply, “I do too,” you're saying you share that feeling. If someone announces they're going to the library, you might say, “Can I come too?”

The word also means “excessively” or “more than enough,” often pointing to a problem. When something is too hot, it's hotter than comfortable or safe. When you have too much homework, you have more than feels manageable. A cake can be too sweet, a joke can be too mean, or a room can be too crowded. In this sense, too acts like a warning light, signaling that something has crossed from good to excessive.

Don't confuse too with to (which shows direction or purpose, like “going to school”) or two (the number). All three sound identical but work completely differently. When you're writing and need the “also” or “excessive” meaning, reach for too with its extra “o,” as if that extra letter represents the “extra” quality the word describes.