one

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Being a single entity, unit, object, or living being.
2. adj. Characterized by unity; undivided: They spoke with one voice.
3. adj. Of the same kind or quality: two animals of one species.
4. adj. Forming a single entity of two or more components: three chemicals combining into one solution.
5. adj. Being a single member or element of a group, category, or kind: I'm just one player on the team.
6. adj. Being a single thing in contrast with or relation to another or others of its kind: One day is just like the next.
7. adj. Occurring or existing as something indefinite, as in time or position: He will come one day.
8. adj. Occurring or existing as something particular but unspecified, as in time past: late one evening.
9. adj. Informal Used as an intensive: That is one fine dog.
10. adj. Being the only individual of a specified or implied kind: the one person I could marry; the one horse that can win this race.
11. n. The cardinal number, represented by the symbol 1, designating the first such unit in a series.
12. n. A single person or thing; a unit: This is the one I like best.
13. n. A one-dollar bill.
14. pro. An indefinitely specified individual: She visited one of her cousins.
15. pro. An unspecified individual; anyone: "The older one grows the more one likes indecency” ( Virginia Woolf).
16. idiom. at one In accord or unity.
17. idiom. one and all Everyone.
18. idiom. one by one Individually in succession.

Century Dictionary and Cyclopedia

1. Being but a single unit or individual; being a single person, thing, etc., of the class mentioned; noting unity: the first or lowest of the cardinal numerals.
2. Being a single (person or thing considered apart from, singled out from, or contrasted with the others, or with another); hence, either (of two), or any single individual (of the whole number); this or that: as, from one side of the room to the other.
3. Some: used of a single thing indefinitely.
4. Single in kind; the same: as, they are all of one age.
5. Single; unmarried.
6. Certain; some: before the name of a person hitherto not mentioned, or unknown to the speaker. As thus used, one often implies social obscurity or insignificance, and thus conveys more or less contempt.
7. Alone; only: following a pronoun and equivalent to self: used reflexively.
8. [By a peculiar idiom, the adjective one was formerly used before the article the or an, or a pronoun, followed by an adjective, often in the superlative (as “one the best prince”), where now the pronoun one, followed by of and a plural noun (partitive genitive), would be used (as “one of the best princes”). Compare the idiom in “good my lord,” etc.
9. A matter of indifference; of no consequence.
10. Completely; entirely; out and out.
11. Identical with; the same as.
12. n. The first whole number, consisting of a single unit; unity.
13. n. The symbol representing one or unity (1, I, or i).
14. n. The same.
15. A single person or thing; an individual; a person; a thing; somebody; some one; something. It is used as a substitute for a noun designating a person or thing, and is in so far of the nature of a personal pronoun, but is capable, unlike a personal pronoun, of being qualified by an indefinite article, an adjective, or other attributive: as, such a one, many a one, a good one, each one, which one. It is used in the plural also: as, I have left all the bad ones.
16. The most frequent constructions of one are — As antecedent to a relative pronoun, one who being equivalent to any person who, or to he who, she who, without distinction of gender.
17. As a substitute for a noun used shortly before, avoiding its repetition: as, here are some apples; will you take one? this portrait is a fine one.
18. After an adjective, as substitute for a noun easily supplied in thought, especially being, person, or the like.
19. It easily passes, however, from the meaning ‘any one’ into the collective sense of ‘all persons,’ ‘people generally,’ and for this can be substituted people, they, we (if the speaker does not except himself from the general statement), you (the person addressed being taken as an example of others in general), or the impersonal passive may be substituted: as, one cannot be too careful (we cannot, you cannot, they cannot, people cannot be too careful); one knows not when (it is not known when). One is sometimes virtually a substitute for the first person, employed by a speaker who does not wish to put himself prominently forward: as, one does not like to say so, but it is only too true; one tries to do one's best. One's self or oneself is the corresponding reflexive: as, one must not praise one's self.
20. [capitalized] A certain being, namely the Deity; God: the name being avoided from motives of reverence or from reserve.
21. Alone; only.
22. To make one; unite into a whole; join.
23. In chem., a termination of hydrocarbons belonging to the series which has the general formula C_nH_2n-4: as, pentone, C₅H₆.

Wiktionary

1. A numerical value equal to 1; the first number in the set of natural numbers (especially in number theory); the cardinality of the smallest nonempty set. Ordinal: first.
2. The ordinality of an element which has no predecessor, usually called first or number one.
3. pro. one thing (among a group of others); one member of a group
4. pro. any person (applying to people in general)
5. n. The neutral element with respect to multiplication in a ring.
6. n. The digit or figure 1.
7. n. A one-dollar bill.
8. n. One run scored by hitting the ball and running between the wickets; a single.
9. n. A particularly special or compatible person or thing.
10. adj. Of a period of time, being particular; as, one morning, one year.
11. adj. Being a single, unspecified thing; a; any.
12. adj. Sole, only.
13. adj. Whole, entire.
14. adj. In agreement.
15. adj. The same.
16. adj. Being a preeminent example.
17. adj. Being an unknown person with the specified name.

GNU Webster's 1913

1. adj. Being a single unit, or entire being or thing, and no more; not multifold; single; individual.
2. adj. Denoting a person or thing conceived or spoken of indefinitely; a certain. “I am the sister of one Claudio” [Shak.], that is, of a certain man named Claudio.
3. adj. Pointing out a contrast, or denoting a particular thing or person different from some other specified; -- used as a correlative adjective, with or without the.
4. adj. Closely bound together; undivided; united; constituting a whole.
5. adj. Single in kind; the same; a common.
6. adj. Single; unmarried.
7. n. A single unit.
8. n. A symbol representing a unit, as 1, or i.
9. n. A single person or thing.
10. Any person, indefinitely; a person or body.
11. v. To cause to become one; to gather into a single whole; to unite; to assimilite.

WordNet 3.0

1. adj. indefinite in time or position
2. adj. eminent beyond or above comparison
3. n. the smallest whole number or a numeral representing this number
4. adj. being a single entity made by combining separate components
5. adj. used of a single unit or thing; not two or more
6. adj. having the indivisible character of a unit
7. adj. of the same kind or quality
8. adj. used informally as an intensifier
9. n. a single person or thing