Obsessive means thinking about something so much and so constantly that it takes over your mind and interferes with everything else. When someone is obsessive about keeping their room clean, they can't relax if a single toy is out of place. When a person becomes obsessive about a video game, they think about it during dinner, during homework, and even while trying to fall asleep.

The word comes from obsess, which means to preoccupy someone's thoughts completely. Being obsessive goes beyond simply caring about something or working hard at it. A student who studies diligently for a spelling bee is dedicated and focused. A student who can't sleep, skips meals, or think about anything else because of the spelling bee has become obsessive.

Sometimes obsessive behavior shows up as repeated actions someone feels compelled to do. An obsessive hand-washer might wash their hands fifty times a day, even when they're already clean. An obsessive organizer might spend hours arranging books by height, then by color, then by author, never feeling satisfied.

Being passionate about something you love, whether it's soccer, drawing, or building with LEGO, is healthy and wonderful. Obsessive means that passion has gotten out of balance and started to hurt rather than help you.