As it turns out the term molygamy does not exist in the dictionary. Nearest words that found are "polygamy" and "monogamy".
Polygamy is the practice or condition of having more than one spouse, especially wife, at one time. Monogamy on the other hand is the practice of marrying only once during life; marriage with only one person at a time.
The term "- gamy" is a word-forming element which means "marriage" in anthropology and "fertilization" in biology; from Greek -gamia, from gamos "marriage". The prefix poly- means "many" or "much", while mono- means “alone,” “single,” or “one”.
Prefixes and suffixes are sets of letters that are added to the beginning or end of another word. They are not words in their own right and cannot stand on their own in a sentence: if they are printed on their own they have a hyphen before or after them.
Learn more about prefixes and suffixes including its uses at Enchantedlearning.com.