IPA: /ˌdaɪəgˈnoʊzəbl/
KK: /daɪəgˈnoʊzəbl/
Able to be identified or determined through examination or testing.
The doctor said the illness is diagnosable with the right tests.
Diagnosable → It is formed from "dia-" (meaning through or across) and "gnosis" (from Greek "gnōsis", meaning knowledge). The suffix "-able" (meaning capable of) indicates that something can be known or identified. Thus, "diagnosable" refers to something that can be identified or understood through knowledge.
Think of 'knowledge' ('gnosis') that helps you understand something 'through' ('dia-') — that's why something 'diagnosable' can be identified.