The paper proves Sino-Vietnamese morphemes do not combine only with SinoVietnamese ones but also with non-Sino-Vietnamese such as pure Vietnamese or even Indo-European, especially French borrowings. The case is not an exception particularly for Vietnamese: similar hybrid words can also be found in other Sino-xenic (Japanese, Korean) and Indo-European languages. Grammatical behaviours of Sino-Vietnamese morphemes show that in noun phrases, sometimes they obey Vietnamese grammatical rules, i.e. [head + modifier(s)], but on the contrary, Vietnamese adopts Chinese grammatical rules. i.e. [modifier(s) + head]. Are the grammatical behaviours related to semantics and, to some extent to phonology? An effort is made to resolve semantic issues based on grammar: synonyms are divided into two kinds: One is "absolute synonyms" and the other is "non-absolute synonyms" according to the criterion [+ or - able to commute each other absolutely]. The effort is not successful because free Sino-Vietnamese morphemes have a double status: they can combine both with other Sino-Vietnamese and with pure Vietnamese, whereas their pure Vietnamese synonyms cannot usually combine with Sino-Vietnamese. It is remarkable that Sino-Vietnamese morphemes with lower productivity tend to be merged into (most) homonymous (Sino-Vietnamese or pure Vietnamese) morphemes with higher productivity.