Being a single unit, or entire being or thing, and no more; not multifold; single; individual.
- Being a single entity, unit, object, or living being.
- Characterized by unity; undivided: They spoke with one voice.
- Of the same kind or quality: two animals of one species.
- Forming a single entity of two or more components: three chemicals combining into one solution.
- Being a single member or element of a group, category, or kind: I'm just one player on the team.
- Being a single thing in contrast with or relation to another or others of its kind: One day is just like the next.
- Occurring or existing as something indefinite, as in time or position: He will come one day.
- Occurring or existing as something particular but unspecified, as in time past: late one evening.
- Informal Used as an intensive: That is one fine dog.
- Being the only individual of a specified or implied kind: the one person I could marry; the one horse that can win this race.
- The cardinal number, represented by the symbol 1, designating the first such unit in a series.
- A single person or thing; a unit: This is the one I like best.
- A one-dollar bill.
- An indefinitely specified individual: She visited one of her cousins.
- An unspecified individual; anyone: "The older one grows the more one likes indecency” ( Virginia Woolf).
- at one In accord or unity.
- one and all Everyone.
- one by one Individually in succession.