Refers to a relationship or tie between things. Most often encountered in the adverbial phrase 因みに (by the way), which signals a related remark.
See also: ちなみに
I wonder if there is some connection between these two incidents.
I looked into the connection between this place name and the legend.
Archaic or literary use for a vow, especially a marriage pledge. Rare in modern Japanese; the common word for promise is 約束.
In old documents, words swearing a marital pledge to the gods are recorded.
約束 is the ordinary modern word for a promise, while 因み in this sense (a pledge, especially a marriage vow) is archaic and rarely used today.
縁 stresses a fated or personal bond between people or things, whereas 因み is a broader, more literary word for any link or association.
by the way; incidentally
Standard kanji spelling; commonly seen in the set phrase 因みに.
Kana spelling is common in casual writing and when used as a standalone noun.
Derived from the verb 因む (ちなむ, to be associated with). The noun form 因み nominalizes this connection, while the adverbial 因みに developed from the continuative form plus the particle に.