Friendship is unlike any other relationship in a person’s life. It can be difficult to define and may carry different meanings for different people. Two friends may describe the degree of their relationship in totally different ways.

While family bonds are typically considered unconditional, friendships are voluntary and thus subject to being set aside when people enter adulthood and “more important” events arise.

Researcher Emily Langan studies friendship. She speaks with Here & Now’s Meghna Chakrabarti about its importance in human development and how it changes over time.