Etymology
Advertisement
an 
indefinite article before words beginning with vowels, 12c., from Old English an (with a long vowel) "one; lone," also used as a prefix meaning "single, lone" (as in anboren "only-begotten," anhorn "unicorn," anspræce "speaking as one"). See one for the divergence of that word from this. Also see a, of which this is the older, fuller form.

In other European languages, identity between the indefinite article and the word for "one" remains explicit (French un, German ein, etc.). Old English got by without indefinite articles: He was a good man in Old English was he wæs god man.

In texts of Shakespeare, etc., an as a word introducing a clause stating a condition or comparison conjunction is a reduced form of and in this now-archaic sense "if" (a usage first attested late 12c.), especially before it.
Related entries & more 
Advertisement
anechoic (adj.)
1948, in electronics, from an- (1) "not" + echoic.
Related entries & more 
anisotropic (adj.)
"not having the same properties in all directions," 1854; see an- (1) "not" + isotropic.
Related entries & more 
anamniotic (adj.)
1880, "without an amnion" (of amphibians and fishes); from an- (1) "not, without" + amniotic.
Related entries & more 
anisometric (adj.)
"of unequal measurement," 1850, perhaps based on German anisometrisch (by 1836); see an- (1) "not" + isometric.
Related entries & more 
Advertisement
anomphalous (adj.)
"without a navel," 1742, from Latinized compound of Greek an- "without" (see an- (1)) + omphalos "navel" (see omphalos).
Related entries & more 
anuria (n.)
"absence of urination," 1838, medical Latin, from Greek an- "not, without" (see an- (1)) + ouron "urine" (see urine) + abstract noun ending -ia.
Related entries & more 
aniso- 
word-forming element meaning "unequal, not equal," from Greek anisos "not equal," from an- "not" (see an- (1)) + isos "equal to, the same as" (see iso-).
Related entries & more 
anaphrodisiac (adj.)
"diminishing the sexual appetite," 1823, from Greek anaphroditos "without sexual desire," or from an- (1) "not, without" + aphrodisiac. Related: Anaphrodisia; anaphroditic; anaphroditous.
Related entries & more 
Siouan (adj.)
1885, from Sioux + -an. Replacing Dakotan.
Related entries & more