IPA: /ˌɪnəˈpɔːrtʃuːnəs/
KK: /ɪnˌɑːpərˈtunəns/
The quality of being unsuitable or occurring at an inconvenient time.
The inopportuneness of his arrival made the meeting awkward.
Inopportuneness → It is formed from "in-" (meaning not), "opportunus" (from Latin, meaning suitable or favorable), and "-ness" (meaning the state of being). The word describes the state of being not suitable or favorable, indicating an untimely or inappropriate situation.
Think of 'not' ('in-') being combined with 'suitable' ('opportunus') to remember that 'inopportuneness' refers to a situation that is not suitable or timely.