Something that costs nothing is free. We can also say that someone is free of pain, which means they have none.
This word has many meanings. On Mondays, admission to some museums is free — there's no charge. Often, people say the best things in life are free, usually meaning love and friendship. We live in a free country, which means we have a lot of rights and freedoms, such as freedom of the press. The word has a similar meaning when we say a prisoner goes free, or philosophers talk about free will: the belief that we make our own decisions, not ones forced on us by society, culture, or a higher power.