A Small Gesture
A lonely person's pity meter is a finely tuned instrument. There is no greater kindness than not extending an overly magnanimous invitation that makes her feel like the neighborhood charity case. A small gesture—an offhand invitation to lunch—is often a better antidote.

Dinner and a Movie
Some people are so debilitated by loneliness that they can hardly discuss it (or anything else). Inviting a friend to a concert or movie will give you something to talk about over dinner.

Prescription for Success
Offer to accompany her to a medical appointment. One study found that doctors said they treat socially isolated people less well than patients with supportive families, and they've seen other health practitioners do the same.

Don't Cancel
Try not to reschedule plans or cancel at the last minute. Lonely people tend to see social engagements as life buoys in a long week; canceling can leave them feeling unmoored.

Checking In
Leave a message. A voicemail or e-mail can make her feel she hasn't been forgotten.

Reality Check
Since research shows that the lonely tend to remember more details about their social encounters and often interpret remarks and nonverbal messages negatively, you might give her a different interpretation of her officemates' behavior or be her reality check at a party.

She's Not Your Wingman
Do not abandon her at the buffet! Dragging your friend to a party might seem like a good idea—she'll get out of the house and meet people—but throwing your friend into a clutch of cheese-straw-wielding revelers by herself while you catch up with other guests is almost guaranteed to leave her feeling worse than before.

Help Her Find Her Place of Comfort
Remind your friend that doing things alone—going to a movie, eating out—is hard for a lot of people, especially the first time. You might take her to the coffee shop that gives you a sense of community when you're on your own and volunteer to help find a place in her neighborhood.

Invitation is Welcome
If you're part of a couple, don't let that stop you from inviting your single friend to join the two of you for dinner or a Saturday outing to Ikea. One O editor says that in her post-divorce despair, some of her happiest, least fraught times were with her married friends who just asked her to show up, plop down on the sofa, drink a little wine and stay for dinner.

Take the quiz: Determine your own loneliness quotient