Current text

As an international dictionary, Wiktionary is intended to include “all words in all languages”.

General rule

A term should be included if it's likely that someone would run across it and want to know what it means. This in turn leads to the somewhat more formal guideline of including a term if it is attested and idiomatic.

“Terms” to be broadly interpreted

A term need not be limited to a single word in the usual sense. Any of these are also acceptable:

Compounds and multiple-word terms such as post office.
Idioms such as go on and give up the ghost.
Proverbs
Abbreviations, acronyms, and initialisms such as NBA.
Prefixes and suffixes such as re- and -ist.
Characters used in ideographic or phonetic writing such as 字 or ʃ.

Proposed text

As an international dictionary, Wiktionary is intended to include 'all words in all languages', as well as all other terms that are idiomatic.

General rules

A term should be included if:

It's attested, and
If it's a multi-word term, it is idiomatic.

'Terms' to be broadly interpreted

A term need not be limited to a single word in the usual sense. Any of these are also acceptable:

Compounds and multiple-word terms such as post office.
Idioms such as go on and give up the ghost.
Proverbs, such as the grass is always greener on the other side.
Abbreviations, acronyms, and initialisms such as NBA.
Prefixes and suffixes such as re- and -ist.
Characters used in ideographic or phonetic writing such as 字 or ʃ.