Serial polygamy is a form of marriage in which participants have more than one sexual partner in their lifetime (hence polygamy), but not at the same time (hence serial). It was coined as a counterpart of polygamy, which traditionally refers to having more than one partner at the same time (in parallel). Within Western culture, this form of polygamy is considerably more prevalent than monogamy (i.e. having only one partner in an entire life, hence monogamy), although the latter is still generally viewed as an ideal or even as a social norm. Matrimony redirects here. ... The term polygamy (many marriages in late Greek) is used in related ways in social anthropology and sociobiology and sociology. ... Monogamy is the custom or condition of having only one mate during a period of time. ...
More generally, any animals (including humans) that do not mate with one partner for life can be considered "serially polygamous", this including those who mate with another only upon the death of a spouse. In more common usage, sometimes derogatorily, serial polygamy tends to refer to a more unstable marriage/divorce series in a person's lifetime.
Although used as a popular synonym for "serial polygamy", the expression "serial monogamy" is inaccurate, as the serial/parallel opposition is centered around the term "polygamy" (there is no such thing as "parallel monogamy" contrasting "serial monogamy"; essentially, neither qualifies as "monogamy"). In addition, attributes like "serial" and "parallel" make sense only when describing multiple relationships, so they cannot logically refer to "monogamy", which implies only one relationship.
Serialmonogamy is a form of monogamy in which participants have only one sexual partner at any one time, but have more than one sexual partner in their lifetime.
Serialmonogamy could also be seen as serial, but not monogamous.
It is a form of polygamy wherein the multiple spouses are had "in series" (one after the other) rather than "in parallel" (at the same time).