IPA: /ɪnˈstrʌktɪvnəs/
KK: /ɪnˈstrʌktɪvnəs/
The quality of providing useful information or teaching something.
The instructiveness of the lecture helped all the students understand the topic better.
Instructiveness → It is formed from "instruct" (from Latin "instruere", meaning to build up or arrange) and "-iveness" (meaning the quality of). The word "instructiveness" refers to the quality of being instructive or providing instruction.
Think of 'building up' ('instruere') knowledge and the '-iveness' indicating a quality — that's why instructiveness means the quality of providing instruction.