IPA: /ˌrɛkwɪˈzɪt.nəs/
KK: /rɛkwɪzɪtnəs/
The condition of being essential or required for a particular purpose.
The requisiteness of safety measures in construction cannot be overstated.
Requisiteness is formed from "requisite" (from Latin "requisitus", meaning required or necessary) and the suffix "-ness" (meaning the state or quality of). The word refers to the state of being required or necessary.
Think of 'requisite' meaning something that is 'required' and '-ness' indicating a state, so requisiteness means the state of being required.