Friendships play a crucial role in your life. In addition to being one of the most common types of relationships you experience, they are also an important source of emotional security and self-esteem (Rawlins, 1992). They provide a sense of belonging when you’re young, help you solidify your identity during adolescence, and provide satisfaction and social support when you’re elderly (Miller et al., 2007).

What exactly are friendships? Friendships are voluntary interpersonal relationships characterized by intimacy and liking (McEwan, Babin Gallagher, & Farinelli, 2008). Whether casual or close, short– or long–term, friendships have three distinguishing characteristics: they are based on liking, they are created by choice, and their bonds are strengthened through shared interests.

Liking.People feel affection and respect for their friends; in other words, friends are people whom you like (Rubin, 1973). You also enjoy spending time with them (Hays, 1988). At the same time, because friendships are rooted in liking rather than love, you’re not as emotionally attached to your friends as you are to your romantic partners, and you don’t put as many emotional demands on them. Indeed, many people assume that they should be more loyal to and more willing to help romantic partners and family members than their friends (Davis & Todd, 1985). Imagine a friend calls you at work, in tears because her boyfriend has just dumped her. She’s extremely depressed, and you’re worried about her, but you hesitate to leave work early to see her. If it had been your sister who called in the same predicament, you might have been more willing to leave work to make absolutely sure she was OK.

Choice.You have more freedom in choosing your friendships than you do in any other relationship category (Sias et al., 2008). Whether you decide to become friends with someone is a pretty straightforward process: if you both want to be friends, you form a friendship. It’s not always that simple in romantic, family, and workplace involvements. For example, in some cultures, people can choose whom they date or marry. But in others, there may be rules governing such matters—including arranged marriages. In your family, you may be bound to others through involuntary ties, including birth, adoption, or the creation of a stepfamily. In the workplace, you have to work with certain people, whether you like them or not.

Shared Interests.Similarity in interests is the primary force that draws you to your friends (Parks & Floyd, 1996), no matter what your age, gender, sexual orientation, or ethnicity. As a result, friendships are less stable, more likely to change, and easier to break off than family or romantic relationships (Johnson, Wittenberg, Villagran, Mazur, & Villagran, 2003). Why? When your interests and activities change, your friendships may change, too. If you adopt different political or religious beliefs or suffer an injury that prevents you from playing a beloved sport, friendships that were built on previous similarities may evaporate. Of course, some friendships will endure—if you and your friend find new points of commonality—but others will fade away. Indeed, a change in shared interests is one of the most common reasons friendships end (Miller et al., 2007).