adoption follow up

Question

Kavod HaRav, An earlier post asked aquestion about a father's relationship with an adopted daughter. The words yichud and negiah were mentioned. Would you kindly elaborate on your answer? I know that negiah has to do with not touching a woman other than your wife/daughter/mother/grandmother. I don't really know what yichud is, and how it relates to this topic. On a different note, would it be possible to have a glossary (on your web site) of commonly used phrases (e.g. noten taam lifgam, etc). This would, for people like me, make the Q & A even more of a learning experience. As always, thank you so much for your tremendous efforts and teachings.