IPA: /ˈtrʌbəlˌsʌmnəs/
KK: /ˈtrʌbəlˌsʌm.nəs/
The state of causing problems or difficulties.
The troublesomeness of the project made it hard to complete on time.
Troublesomeness → It is formed from "trouble" (from Old French *trouble*, meaning disturbance or confusion) and "-some" (meaning characterized by) and "-ness" (meaning the state of). The word "troublesomeness" refers to the state of being characterized by trouble or causing difficulty.
Think of 'trouble' as a disturbance, and when something is 'characterized by' that trouble ('-some'), it leads to a state of causing difficulty ('-ness').