1. An arithmetical value, expressed by a word, a symbol, or a figure, representing a particular quantity and used when figuring up and making calculations and for showing the order in a series or for identification: Ted's biology teacher dialed the phone number so she could tell the bookstore the number of textbooks she wanted to order for her students.
2. A collection of individual things which can be added up and referring to things that are physically or which are symbolically separate, not merely separable into units: The symbols 1, 2, 3, 4, 5, etc. and the words, one, two, three, four, five, etc. are numbers.

An "amount" emphasizes the whole, while a number focuses on the parts; such as, an "amount" of money; a number of coins.

A "quantity" stresses measurement in bulk (a bunch of apples are in the bag), a number stresses individual items (six apples are on the plate).

When Jacob moved to a smaller apartment, a number of his books had to be given away to the local library.

A number of seats are still available at the theater.

Numbers of people complained when the proposed shutdown of the local grocery store was announced.

3. In grammar, a word form that indicates one person or thing or refers to more than one: The numbers used in grammar are "singular" (one) and "plural" (two or more).

1. To specify an amount or quantity: The investors in the company numbered in the thousands.
2. To include or to classify as a member of a group: The university numbers 2,000 students that are attending classes so far this year.

The population of the town now numbers 10,000.

3. To indicate a position in a series: Each document was numbered in a sequence.
4. To identify people or things in a series: Maude numbers the times that she does each exercise at the fitness studio.

Mrs. Jackson told her students to take out a sheet of paper and to number it from 1 to 15 down the side for the quiz.

Dr. Herbert Kyle was numbered by his students as one of the best professors in the university.

One of the harmonic elements in mathematical expressions and formulas for the forces and strong currents of the oceans: As an oceanographer, it was Hickory's responsibility to calculate the astronomical tidal constituent in the local harbor.

A number that indicates a principal quantity: Cardinal numbers are the primary "one", "two", "three", "four", etc. as opposed to ordinal numbers "first", "second", "third", "fourth", etc.

The number of very small particles and associated neutrinos minus the number of positrons and associated antineutrinos: As an engineer, Mildred made a careful study of the electron lepton numbers during her analysis of colliding atoms in the air, noting that they were generating more electrons as well as x-rays and gamma rays.

The quantity of negative charges in atoms or ions: Jack and all the other chemistry students had to memorize the electron numbers from the chart that the teacher presented to them.

Emerging Technology, Part 2, Parts 1-10.

Intenational Standard Book Number number: The use of ISBN followed by the word number is an excessive use of the word.