association
A group of people joined together for a shared purpose.
An association is a connection between two things, or a group of people who've joined together for a shared purpose.
When you hear a song that reminds you of summer vacation, that's an association: your brain links the music with those memories. If the smell of cinnamon makes you think of your grandmother's kitchen, you've formed an association between that scent and those happy times. Our minds constantly create these connections, helping us make sense of the world and remember important things.
The word also means an organized group. A neighborhood association brings together people who live in the same area to solve local problems or plan community events. The National Basketball Association (NBA) is a group of professional basketball teams that have associated themselves, agreeing to follow the same rules and compete in the same league. Teachers might form an association to share ideas and support each other's work.
When you associate with someone, you spend time with them regularly. The verb form is associate, and someone who belongs to an association is called a member or an associate.