The Boston Young Professionals Association (bostonypa.com) caters to members 45 and under.
The Boston Ski & Sports Club (bssc.com) runs teams and hosts social events, says most of its members are 21 to 40.
Boston Event Guide (bostoneventguide.com) is hosting a Spring Cocktail Party and Dance, which caters to "young professionals" in their 30s and 40s, on Thursday.
Onein3 Boston (onein3boston.org), the Boston Redevelopment Authority program that aims to help young people have good lives in the city, says it defines "young professionals" as 20- to 34-year-olds.
Social Boston Sports (socialbostonsports.com), a group for young professionals that's been around for a little over a year, says by "young professionals," it means 21 to 35.