diagnostic
adj.adj. used to find out the cause of a problem or to check how much someone knows. You use this when you want to identify a specific illness, a computer error, or a student's level.
adj. relating to the identification of the nature or cause of a phenomenon, typically in medical, technical, or educational contexts. Often describes tools or tests used to establish a baseline or pinpoint a fault.
The doctor ordered a diagnostic test to check his heart.
Teachers use a diagnostic assessment at the start of the year to see which grammar points students already understand.
The software includes a diagnostic suite that monitors system performance in real time to identify potential hardware failures before they cause a total crash.
From Ancient Greek διαγνωστικός (diagnōstikós), adjective from διαγιγνώσκω (diagignṓskō, “to distinguish, diagnose”).
Typically precedes the noun it modifies; frequently collocated with 'test', 'tool', or 'procedure'.