Actually not to be a total grammer geek but...
'one'
Definitions
single; lone; not two or more ⇒ "one car"
(as pronoun) ⇒ "one is enough for now", "one at a time"
(in combination) ⇒ "one-eyed", "one-legged"
distinct from all others; only; unique ⇒ "one girl in a million"
(as pronoun) ⇒ "one of a kind"
a specified (person, item, etc) as distinct from another or others of its kind ⇒ "raise one hand and then the other"
(as pronoun) ⇒ "which one is correct?"
a certain, indefinite, or unspecified (time); some ⇒ "one day you'll be sorry"
(informal) an emphatic word for a1, an1 ⇒ "it was one hell of a fight"
a certain (person) ⇒ "one Miss Jones was named"
pronoun
an indefinite person regarded as typical of every person ⇒ "one can't say any more than that"
any indefinite person: used as the subject of a sentence to form an alternative grammatical construction to that of the passive voice ⇒ "one can catch fine trout in this stream"
(archaic) an unspecified person ⇒ "one came to him"
noun
the smallest whole number and the first cardinal number; unity See also number (sense 1)
a numeral (1, I, i, etc) representing this number
(informal) a joke or story (esp in the one about)
(music) the numeral 1 used as the lower figure in a time signature to indicate that the beat is measured in semibreves
something representing, represented by, or consisting of one unit
Also called: one o'clock. one hour after noon or midnight
a blow or setback (esp in the phrase one in the eye for)
One is a lot of things