guild also gild 
(gĭld)
(gĭld)n.
1.
a. An association of persons of the same trade or pursuits, formed to protect mutual interests and maintain standards.
b. A similar association, as of merchants or artisans, in medieval times.
2. Ecology A group of species in a community that use similar environmental resources in a similar way, such as a group of songbirds that all glean insects from leaves.
[Middle English gild, from Old Norse gildi, payment, guild.]