This is a question about Mandarin as much as it is about Memrise--although the two are related. Is there a fully authoritative reference for tones in Mandarin? I understand that as a language there are regional deviations. However, Memrise as far as I can tell has no mechanism for alternate pinyin like they do for English and written Chinese. This comes up because sometimes two-character words cause the second character to take on the 5th tone, when it doesn't as a single character. When spoken, these ambiguities are almost imperceptible. However, in the harsh light of Memrise testing, the system forces one to memorize it--and I wonder if that's a waste of time since the goal (presumably) is actually learning Chinese.