IPA: /ˌsɛmɪˈdɑːrk.nəs/
KK: /sɛmiˈdɑrk.nəs/
A state of being partially dark, where there is some light but not enough to see clearly.
The room was filled with semidarkness, making it hard to read the book.
Semidarkness → It is formed from "semi-" (meaning half) and "darkness" (from Old English "deorc", meaning absence of light). The word "semidarkness" refers to a state that is half dark or partially lacking light.
Think of 'semi-' meaning half, and 'darkness' referring to the absence of light — semidarkness is a state that is half dark.