We've assembled this glossary to help explain some key terms related to social capital, civic engagement and social networks. If there are other words that you see on our website that need explaining, please e-mail us.

Astroturf social capital/Astroturf grassroots efforts:   Apparently real grassroots efforts that are in reality largely funded by an organization (often a corporation). Astroturf associations or astroturf grassroots efforts give the appearance that a corporate viewpoint is widely held by a large number of independent individuals.

Asymmetrical relationships:   See directed social networks.

Bonding social capital:   Social ties that link people together with others who are primarily like them along some key dimension. For example, a group that meets of 50-year old African American men. [In reality some groups are bonding in some ways and bridging in others: for example, the Knights of Columbus is bonding with respect to religion, but bridging across social class.] In general one's social support (e.g., people who bring you chicken soup when you're sick or visit you in the hospital) tend to be your bonding social capital. Bonding social capital is generally easier to build than bridging social capital.

Bridging social capital:   Social ties that link people together with others across a cleavage that typically divides society (like race, or class, or religion).

Centrality: (from social networks literature) A measure of how important a node (actor) is to connecting members of a social network, i.e., the degree to which a node (or actor) is a 'sociometric star' or 'isolate'. The formulas for this vary depending on whether one is talking about directed (asymmetric) social networks or undirected (symmetric) social networks.

Check-writing organization:   As distinct from a truly active membership organization (where members regularly meet, and elect representatives), a check-writing organization is one where most members' membership consists of writing a check to that organization for annual dues. 'Check-writing organizations' are often headquartered in Washington, DC, and staffed by professional members. There is obviously much more chance to create social capital through an active membership organization than through a check-writing one.

Closure: (from social networks literature) Can be seen as the opposite of structural holes. The degree of likelihood that everyone in a network knows everyone else in the network, or the likelihood that if A knows B and B knows C that A knows C. Can also see this as the degree of connectedness of a social network.

Clustering: (from social networks literature) The degree to which a social network can be defined by clear sub-networks. For example, if all the employees at a company over age 45 hung out together and all the employees under age 45 hung out together, there would be clustering of the network around age.

Degrees of separation:   The shortest number of path links it takes to get from person (or node) X to person (or node) Y in a network. For example, if X knows A who knows B who knows Y, then X and Y have three degrees of separation (X to A, A to B, and B to Y). A study by Stanley Milgram in the 1950s testing how many links it took to connect a random mid-Westerner from Omaha or Wichita with a random person from Boston seemed to show that subjects were on average 6 path links away from each other. [Each recipient of a letter was supposed to send to the target recipient if he/she knew the target directly, or forward on the person who the subject thought would be most likely to know the target; this procedure was iterated and the number of links were totalled.] This has been generalized into the claim that any two people in the world are 6 degrees separated, although Milgram never used the phrase 'degrees of separation. Still, the Milgram methodology has been criticized by some. Milgram's findings were recently tested in a Small World experiment by Duncan Watts at Columbia, which has found an average path length of worldwide volunteers of five, although there are some problems with their methodology.

Density: (from social networks literature) The percentage of potential relationships that actually exist in a social network. Relationships are ordered, so the fact that A considers B to be his/her friend does not mean that B considers A to be his/her friend. The number of potential ordered relationships in a social network with N nodes equals n times n-1. The higher the density the more likely that any two random people chosen from a social network will have a social tie.

Directed social networks:   (from social networks literature) In directed social networks, as distinct from undirected social networks, there is no assumption that if A regards B as his/her friend, that B regards A as his/her friend. Often friendships are symmetric, but they need not be, and in relationships with powerful or popular people, more people may feel that they are friends with this powerful/popular person than he/she feels are really his/her friend. Also called asymmetric social networks.

Dyad: (from social networks literature) A relationship between two people, for example A being friends with B.

Formal social capital:   Social ties that exist within the context of a formal organization (with elements like bylaws, regular meetings, minutes, etc.).

Generalized reciprocity:   See reciprocity.

Homophily:   Also called "birds of a feather flock together" -- the sociological phenomenon that people are more likely to form friends with others who are like them in race/ethnicity, social class, education, age, etc. This is what makes bonding social capital easier to build than bridging social capital.

Hubs: (from social networks literature) Individuals (or nodes) in a network that have multiple links leading in/out from them. The individuals (or nodes) that have the largest number of links in/out are the largest hubs. For example, airline flights can be seen as links in and out of cities (where the cities are nodes). If a town only had one flight in a day, it would not be a hub, but if a town had multiple flights in/out from multiple locations, it would be a hub.

Informal social capital:   Social ties that exist outside the context of formal organizations (like neighbors talking over a back fence, ties through a pick-up basketball game, etc.).

Instrumental social capital:  Social ties built with some purpose in mind (like improving schools, decreasing community crime, etc.).

Linking social capital:   A social tie (often a bridging social tie) to those with power that provides one with the capacity to gain access to resources, ideas and information from formal institutions beyond the community.

Links: (from social networks literature) In any network or social network, the network consists of things or people (the nodes) and links which characterize the social relationships between two nodes and show the relational ties.

"Links in" versus "links out":   (from social networks literature) Relationships do not have to be symmetrical. For example in web page links, site A might have a link to site B, but site B needn't necessarily have a hyperlink to site A. A link from B to A would be an 'in link' for A. The number and prevalence of in links can be taken as a sign of one's reputation. Out links can be taken as an effort for outreach or collaborativeness.

Macher: A dimension of social capital we found in our Social Capital Community Benchmark Survey in 2000, as distinguished against 'schmoozing,' that measured one's formal involvement and leadership in community (such as serving as an officer or committee member of group, etc.).

Multi-stranded ties: Social ties based on knowing an individual through multiple channels (for example, a voluntary association, living in the same neighborhoods, participating in a sports league with them, etc.).

Netroots: A portmanteau from 'interNET grassROOTS' describing online political activism organized through blogs and other online advocacy groups.

Networks: Social capital concerns the value of social relationships which are found in social networks, but networks can be used more generally to show the relationships and links between nodes. For example, networks can show which roads connect which towns, or which computers in a network are attached to which printers, or which websites have links out or links in to which other websites.

Nodes: (from social networks literature) The entities whose inter-relationships a social network or network helps explain. Any network or social network consists of things or people (the nodes) and links which characterize the relational ties between these nodes. Nodes could be people (in a social network) or cities (in a network depicting airline flights or a network showing inter-city roads).

Non-reciprocal friend: (from social networks literature) Person A says that he/she is a friend with B but B does not list A as a friend. In contrast to a reciprocal friend or a reciprocal non-friend.

Open dyads: (from social networks literature) Where A is friends with B and B friends with C, but A is not friends with C. [See also dyads.] Open dyads tend over time to become closed and become triads.

Power laws: (from social networks literature) Also called scale-free networks. A 'rich get richer' law that explains why in networks, new links are disproportionately added to the sites that already have a larger number of links to/from them. In powerlaw networks (like a map of airline routes), a few sites can account for a significantly disproportionate share of the total links. Networks with power law dynamics are less prone to random attacks (since most sites are not hubs) but more susceptible to targeted deliberate attacks on hubs. See Albert-Laszlo Barabasi's book Linked. [Note: It is much clearer that power laws can explain non-human networks than social networks, as this blog entry by Thomas Sander posits.]

Private-regarding social capital:  Social ties that exist only from private (often leisure) relationships, such as relationships with neighbors or friends from dinner parties, or relationships from a pick-up basketball game. Private-regarding relationships can evolve into public-regarding social capital (such as if a neighborhood block party became the basis for sustained political action on the part of the neighbors). Also called inward-looking social capital.

Public-regarding social capital:   Social ties in service of some larger public purpose in society, like social relationships that exist through a crime-watch group, or social ties from a youth mentoring program. Public-regarding relationships can still sometimes evolve to support private-regarding social capital (such as if friendships from a political campaign became the basis for a book group). Also called outward-looking social capital.

Reciprocal friend: (from social networks literature) Person A considers B to be his/her friend and B considers A to be his/her friend. In contrast to a reciprocal non-friend or a non-reciprocal friend.

Reciprocal non-friend: (from social networks literature) Person A does not consider B to be his/her friend and B likewise does not consider A to be his/her friend. In contrast to a reciprocal friend or a non-reciprocal friend.

Reciprocity (generalized):  When there is generalized trust within a geographic community or a community of interest, individuals often start displaying reciprocity, doing something for another not with any immediate expectation of return, but trusting that the favors will be passed on to others in the community, and either directly or indirectly benefit the person doing this initial favor. This is in distinction to specific reciprocity.

Scale-free networks: Networks that exhibit power laws.

Schmoozing: Also called informal social ties (friends, neighbors, dinner parties, hanging out in pubs, etc.).

Small world phenomenon:  The fact that there are a huge number of people in the world with most people’s ties relatively localized (i.e., much higher chance that you know someone in your home town than someone all the way across the world). Yet despite the localization of most social ties, everyone appears to be only a few social ties away from everyone else. This can be accomplished if a small percentage of the links are randomized and they effectively shorten the social distance for everyone else. See: Columbia's "Small World Project" and Small Worlds.

Single-stranded ties:   As distinct from multi-stranded ties, social ties based on knowing an individual through only one channel (for example, through work only or only through going to same house of worship).

Social capital:  The value of social networks, partly stemming from the norms of trust and reciprocity that flourish through these networks. For more information on social capital, see the FAQ page.

Social networks:  An enumeration of the relationships that exist between groups of individuals or organizations (i.e., who knows whom). The structure of these networks and the character of these links between those individuals (or nodes), influence such things as how effectively the network can produce various results, its vulnerability, whether the network is well integrated or balkanized, etc. In a schematic social network, the nodes are people and the lines are social ties from one node (person) to another. A simple schematic of a social network can be found here. Social networks can be asymmetrical: i.e., Ann can say that Bob is her friend even if Bob does not say that Ann is her friend.

Social trust: (also called generalized trust) A well-tested question that asks how much strangers can be tested, typically of the form: 'which comes closer to your views, people can generally be trusted or you can’t be too careful in dealing with others?'

Specific reciprocity: Being willing to do a favor for a specific individual or group of individuals (under the theory that it will directly or indirectly benefit you or the community), but not being willing to do such a favor for a stranger (generalized reciprocity).

Strong ties:  Close personal friends; typically the people one goes to in times of great crisis (if one has lost a job, or has marital problems, or has a severe health problem) and needs personal support.

Structural holes: (from social networks literature) The holes in one person's social network that another person has ties to. An individual can obtain power from having social relations with useful contacts that his/her friends do not know.

Thick trust:  Trust embedded in personal relationships that are strong, frequent, and nested in wider networks. This honesty is based on personal experience (see p.136 of Putnam’s Bowling Alone). See also specific reciprocity.

Thin trust: (or social trust or generalized trust) Extends trust beyond an individual’s actual network, into a more implicit sense of common networks and assumptions of eventual reciprocity. Thin trust is based more on community norms than personal experience, therefore if the community connections deteriorate; it too decreases in effectiveness and value. (See p.136 of Putnam’s Bowling Alone.)

Triad: (from social networks literature) A three-way relationship where A, B, and C are all friends with each other.

Trust:  The extent to which individuals believe that others mean what they say and will follow through on their commitments. Like reciprocity, sometimes trust is generalized to strangers and across a wide range of circumstances, and sometimes it is much more specific: e.g., extending to specific person or class of persons around specific action(s) in specific setting(s). People's predictions of whether others can be trusted is probably a measure of others' trustworthiness, not the respondent's gullibility. Respondents reports about whether others could be trusted correlated fairly highly for example with the percentage of lost wallets distributed in those communities that were returned to their owners with the contents intact.

Trustworthiness:  Whether one can be confident that others will act in a trusting manner.

Undirected social networks: (from social networks literature) In undirected social networks, as distinct from directed social networks, it is assumed that any relationship of A to B is also a relationship from B to A.  Also called symmetric social networks.

Weak ties:  More like nodding acquaintances – people to whmo one might be able to go for smaller favors (like asking if they knew of a job, or whether they could lend you a $5) but whom one does not know that well. Mark Granoveter wrote The Strength of Weak Ties to show that it was weak ties rather than stronger ties that were especially useful in things like job searches because close ties quickly turned back on themselves and thus didn't gather information from as large numbers of people.