What is the X in X-mas?
Old English life (dative lif) "existence, lifetime, way of life, condition of being a living thing, opposite of death," from Proto-Germanic *libam (cf. Old Norse lif "life, body," Dutch lijf "body," Old High German lib "life," German Leib "body"), properly "continuance, perseverance," from PIE *leip- "to remain, persevere, continue; stick, adhere" (see leave (v.)). Much of the modern range of meanings was present in Old English. Meaning "property which distinguishes living from non-living matter" is from 1560s. Sense of "vitality, energy" is from 1580s. Extended 1703 to "term of duration (of inanimate objects)."
Life-jacket is from 1840; life-preserver from 1630s of anything that is meant to save a life, 1803 of devices worn to prevent drowning. Life-saver is from 1883, figurative use from 1909, as a brand of hard sugar candy, from 1912, so called for shape. Life-form is from 1861. Life cycle is from 1855.
n. pl. lives (līvz)
The property or quality that distinguishes living organisms from dead organisms and inanimate matter, manifested in functions such as metabolism, growth, reproduction, and response to stimuli or adaptation to the environment originating from within the organism.
The characteristic state or condition of a living organism.
Living organisms considered as a group.
A living being, especially a person.
generally of physical life (Gen. 2:7; Luke 16:25, etc.); also used figuratively (1) for immortality (Heb. 7:16); (2) conduct or manner of life (Rom. 6:4); (3) spiritual life or salvation (John 3:16, 17, 18, 36); (4) eternal life (Matt. 19:16, 17; John 3:15); of God and Christ as the absolute source and cause of all life (John 1:4; 5:26, 39; 11:25; 12:50).