Are R' Menashe Klein's volumes of responsa pronounced "Mishna Halachos" or "Mishaneh Halachos"? Can someone provide the grammatical explanation please?
Mishne Halachos, "a summary of halachos" like in Mishne Tora, "a summary of Torah". The root is shin-nun-he: it's related to shana, "repeated".
I've heard that after he allowed certain eruvin that R' Moshe Feinstein did not, people jokingly (and with quite a lack of k'vod hatora) referred to his books as M'shane Halachos, "changer of halachos". The root is shin-nun-he, in piel, shina, "changed".