A unique number which identifies a published book, for example, an ISBN.

plural of book number

(number theory) A positive integer whose abundancy index is greater than that of any lesser positive integer. / Used other than figuratively or idiomatically: see superabundant, number.

plural of negative number

plural of superabundant number

plural of numbered list

(grammar) A numeral that expresses how many times some event happens.

(spirituality) A number or sequence of numbers that a person frequently notices in the world around them, believed to be a message from benevolent angels.

A number assigned to each work composed by Wolfgang Amadeus Mozart.

(fluid mechanics) A dimensionless number (symbol We) that is useful in analysing fluid flows where there is an interface between two different fluids. It can be thought of as a measure of the relative importance of the fluid's inertia compared to its surface tension.