supplement

Something added to complete a thing, make up for a deficiency, or extend or strengthen the whole.

A section added to a book or document to give further information or to correct errors.

A separate section devoted to a special subject inserted into a periodical, such as a newspaper.

To provide or form a supplement to.

To fill up or supply by additions; add something to, as to a writing, etc.; make up deficiencies in.

An addition to anything, by which it is made more full and complete; particularly, an addition to a book or paper.

Store; supply.

In trigonometry, the quantity by which an angle or an arc falls short of 180° or a semicircle.

Synonyms Appendix, Supplement. An appendix contains additional matter, not essential to the completeness of the principal work, but related to it; a supplement contains additional material, completing or improving the principal work.