A one |
superior; first-rate; first-class. |

atomic number |
the number of protons or positive electrical charges in the nucleus of one atom of a given element. [2 definitions] |

back number |
any previous issue of a periodical. |

call number |
a series of numbers or numbers and letters used to locate a book in a library. |

cardinal number |
any number used to express quantity but not order. (Cf. ordinal number.) |

compose a number |
In mathematics education, to add together different place values to make a complete number. For example, to compose the number 231, you would add the three place values that make up this number, a 200, a 30, and a 1. |

compound number |
a quantity expressed in two different but related units of measure, as dollars and cents or pounds and ounces. |

counting number |
the number one and any number obtained by successively adding one to get the next number. |

decompose a number |
In mathematics education, to separate a number into its component place values. For example, to decompose the number 231 you would write "200+30+1". |

even number |
a whole number that can be divided exactly by 2. |

f-number |
the relative aperture of a camera lens, representing the light it will transmit, which is obtained by dividing the focal length of the lens by the diameter of the aperture. |

Mach number |
(sometimes l.c.) the ratio of the speed of an object, or the flow of a fluid, to the speed that sound travels in the environment in which the object, or fluid, is moving; Mach. |

mass number |
the total number of neutrons and protons in the nucleus of an atom. |

mixed number |
a number consisting of an integer and a fraction, such as two and one half. |

natural number |
any positive integer or zero. |

number line |
a line that displays real numbers according to their distance in a positive or negative direction from a point defined as zero. |

number name |
a name assigned to a quantity, such as one. |

number one |
(informal) oneself or one's own interests. [2 definitions] |

number plate |
(chiefly British) a metal tag or plate displayed on a motor vehicle and bearing a registration number that qualifies the vehicle as legal to drive on public highways and roads; license plate. |

number sentence |
in mathematics education, a simple equation or inequality containing numbers and operators. |