Proto-Indo-European root meaning "beyond."
It forms all or part of: adulteration; adultery; alias; alibi; alien; alienate; alienation; allegory; allele; allergy; allo-; allopathy; allotropy; Alsace; alter; altercation; alternate; alternative; altruism; eldritch; else; hidalgo; inter alia; other; outrage; outrageous; outre; parallax; parallel; subaltern; synallagmatic; ulterior; ultimate; ultra-.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit anya "other, different," arana- "foreign;" Avestan anya-, Armenian ail "another;" Greek allos "other, different, strange;" Latin alius "another, other, different," alter "the other (of two)," ultra "beyond, on the other side;" Gothic aljis "other," Old English elles "otherwise, else," German ander "other."
It forms all or part of: abolish; adolescent; adult; alderman; aliment; alimony; Alma; alma mater; alt (2) "high tone;" alti-; altimeter; altitude; alto; alumnus; auld; coalesce; elder (adj., n.1); eldest; Eldred; enhance; exalt; haught; haughty; hautboy; hawser; oboe; old; proletarian; proliferation; prolific; world.
It is the hypothetical source of/evidence for its existence is provided by: Greek aldaino "make grow, strengthen," althein, althainein "to get well;" Latin alere "to feed, nourish, suckle; bring up, increase," altus "high," literally "grown tall," almus "nurturing, nourishing," alumnus "fosterling, step-child;" Gothic alþeis, Dutch oud, German alt "old;" Gothic alan "to grow up," Old Norse ala "to nourish;" Old Irish alim "I nourish."
also etcetera, early 15c., from Latin et cetera, literally "and the others," from et "and" + neuter plural of ceterus "the other, other part, that which remains," from Proto-Italic *ke-etero‑, from *ke-, variant form of PIE root *ko-, the stem of demonstrative pronoun meaning "this" + *etero‑ "other (of two), again, a second time, again," a PIE adjective of comparison.
The common form of the abbreviation before 20c. was &c., but etc. now prevails.