virtue

Here the word becomes countable, and that is the quickest way to tell it from good conduct in general. Virtue is how one behaves; a virtue is one trait among several. The plural sits naturally with possessives. Laurence Sterne writes of modest men who "take pains to hide their virtues." The singular usually takes a or one: loyalty is a virtue.

The least moral of the senses, because things have virtues too. Daniel Defoe in 1719 has his castaway wonder whether unknown plants "have virtues of their own." A 2011 letter to The Guardian finds "one virtue" even in a policy it attacks. That frame, one virtue of X is…, often grants a single advantage to something otherwise criticized.

The broadest sense carries the word's history. Latin virtus meant "manliness, bravery, worth, moral excellence" and was built on vir, "man", the root behind virile. In English the word pushed aside Old English cræft, which survives as craft. Here it names human goodness as a whole, the thing philosophers argue about, rather than any single trait.

Power that can run out. Robert Southey's wave holds "a virtue" that restores tired limbs. In Madeleine L'Engle's A Wrinkle in Time (1962), "the virtue has gone" from a pair of glasses. The phrase that keeps the sense in daily use is by virtue of, meaning "because of" or "through." The Economist wrote in 2011 of an advantage won "by virtue of discipline and experience."

Angelology borrows the word as the name for a whole rank of heaven, and in that use it is often capitalized. John Milton's Paradise Lost (1667) lists the orders in one breath, "Thrones, Dominations, Princedoms, Virtues, Powers," the way a court lists titles. The link to divine power is direct: these beings are named for the power they embody.