Matrimony denotes the state of those who are united in the relation of husband and wife; marriage denotes primarily the act of so uniting, but is extensively used for the state as well. Wedlock, a word of specific legal use, is the Saxon term for the state or relation denoted by matrimony.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

union It is improper to impose sanctions upon the union.
marriage He intimated that all is not well in his marriage.
wedlock Because he was unemployed, their wedlock failed.
wedding The wedding ceremony was performed in the morning.
nuptials He said nothing about Jessica’s upcoming nuptials.

Popularity over time

Word	1850 → 2019	Trend
matrimony		steady
union		falling
marriage		rising
wedlock		steady
wedding		rising
nuptials		rising

Use in printed books, per decade from 1850 to 2019.

By length

5 letters: union²
7 letters: wedding², wedlock²
8 letters: marriage², nuptials²
10 letters: couverture

The small number after each word is its number of syllables (union² = 2 syllables).