Capable of being believed; credible.

(childish) The quality or act of pretending; acting as if something is true when in fact one knows it is not.

plural of believer

A system of beliefs.

plural of belief system

present participle of make believe

The abstract quality of making believe

In a believable way. / Used to express the speaker's assessment of the credibility of a reported statement.

The state or quality of being believable; believability.

unbelievable