Able to be complained about; worthy of complaint; capable of being the subject of a formal grievance or complaint.
From complain (from Latin complainere, to lament together) + -able (capable of being). The -able suffix indicates something is a possible object or target of the action indicated by the root verb.
The adjective 'complainable' is legalistic and bureaucratic—you see it in institutional policy documents more than everyday conversation. Its existence reveals how formal language creates adjectives for concepts that regular speakers would express differently, like saying 'This is something we can complain about' rather than 'This is complainable.'
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