i Register
In some senses, premature is marked as informal. Watch for register when choosing this word.
adj
Occurring before a state of readiness or maturity has arrived.
a premature birth
premature reports of the singer's death
Taking place earlier than anticipated, prepared for, or desired.
I was lost in reveries of death, and the idea of premature burial held continual possession of my brain.
Suffering from premature ejaculation.
noun
An infant born prematurely.