Work; a number indicating the order in which compositions were composed.

(Latin) Meaning work. Work numbers are usually assigned by the composer. Often the opus numbers are assigned in order of composition, but at times the numbers are assigned by order of publication.

(Latin: 'work') A term is generally used in the listing of a composer's works by opus numbers, usually abbreviated to Op. Since the Latin plural opera would lead to unnecessary confusion it is best avoided, although the alternative opuses remains an unsatisfactory substitute. Opus numbers are not always a guide to the date of composition or even to the date of publication.

Convenient method of numbering a composer’s works where a number follows the word “opus”. For example, Opus 28, No. 4.