単婚 is read as たんこん (tankon) and means monogamy.
たんこん
tankon
たんい
credit (in school)
たんいつ
single
たんこうぼん
standalone book (i.e. not part of an anthology, series, etc.)
たんに
simply
たんなる
mere
たんちょう
monotone
たんご
word
たんすう
singular (number)
たん
singles (tennis, badminton, etc.)
ひとえ
monopetalous
たんさん
(single-industry) industrial union
たんぱつ
firing one shot at a time