When contemporary researchers quantify types, they usually come up with around three or four levels of relationship depth—acquaintances, casual friends, close friends, and intimate or “best” friends.

The 4 Levels of Friendship

Acquaintances are the people we see on a fairly regular basis that we “sort of know,” at least well enough to make idle small talk, but with whom we don’t really have the desire or emotional needed to deepen the connection.

Casual friends are typically those with whom you spend time within shared activities or with whom you cross paths on a regular basis and whom you have gotten to know enough to feel ready to call a “friend.” You might love all the members of your painting class, have a laugh with them during the meetings, and even hang out with them outside of class, but they are people that you probably wouldn’t hang with if you didn’t share this particular activity.

Close friends pretty much always start as acquaintances who turn into casual friends and whom you have enough mutual admiration and affinity that you share a little more of yourself, they share a little more about themselves, and you continue to enjoy getting to know one another and spending time together.

Close friends are the ones that you call when life sucks so bad that you just want to cry, hide, or run away. Close friends are those you trust with many of your secrets and the friends who put up with you even when you’re in a lousy mood or need to talk at 2 am when your love life splits wide open.

Intimate friends are the most intensely connected. These are the friends that you let into the inner sanctum of your heart and mind, who you trust with the deepest secrets, and who you know will never let you down or betray your trust.

Some people form this type of friendship with their partner, but that’s not always the case. One woman describes her close friends are her “soul sisters” and her partner knew that when they married, the “soul sisters” were going to be part of their “family” for life.

Aristotle’s Three Friendship Types

Thousands of years earlier, Aristotle described three types of friendships—utility, pleasure, and good.

Friendships of utility are the friendships some of us would call “friendships of convenience.” These are the folks with whom we share carpool duty, or whose home we keep an eye on while they’re out of town because we’ll need them to pick up our mail when we go on vacation next month. It might be the woman you sit beside on the train everyday: You’d never find any other reason to enjoy her company otherwise, but she’s familiar, pleasant, and safe.

Friends of convenience or utility are the people we rely on and on whom we can rely on for small tasks and a willingness to help out so long as the expectations of investment aren’t too great. Once the needs are no longer present for the assistance to be of value, these relationships are likely to evaporate quickly.

Friendships of pleasure are those friendships that are all about simply enjoying one another’s company and having a good time together. This type of friendship includes the neighbors that you like having drinks with on your deck on summer evenings or the crowd you always get a coffee with after a book club meeting. These are the people you count on to keep your mood light or your mind off your troubles.

They might be the Sunday afternoon football crowd, the monthly Bunco brigade, the moms that you enjoy hanging out with at your kids’ soccer and softball games. They might be the folks who show up at the same parties to which you are invited and who always make you feel welcome. You can spend a lifetime hanging with these types of friends: They bring you , your presence has the same effect on them, and there’s no deeper demands on of either of you. So as long as the friendship continues to be a pleasure, it can endure.

Friendships of the good are friendships based on mutual respect, admiration, and appreciation for the qualities each of you brings to the relationship. These may begin as a function of propinquity, shared interests, or shared life stage, but the spark between the two friends is lit and the opportunity for increasing mutual self-disclosure and connection is harvested.

In a friendship of the good, you value who that friend actually is, strengths and weaknesses alike, and there is sufficient trust between the two that the relationship’s quality and depth outshine those of other types of friendship. These relationships endure and are fed by the mutuality of the esteem and appreciation between the true friends – even if the time between meetings stretches into months or years.

So, How Many Close Friends Do You Truly Need?

Data from a brand new study (Degges-White, in review) of adults from their thirties to their seventies makes it clear that the number of close friends we need to feel that we have enough is somewhere between three and five. Not only that, but adults with four or five friends enjoy the highest levels of life satisfaction and those with three close friends are not far behind. And if you have one person who considers you their best friend, the satisfaction you enjoy in life is significantly higher than those who don’t. So, bear in mind that being there for others and holding a valued friendship place in another’s life can absolutely positively influence your own level of well-being.