Words that begin with 'oblig' are oblige, obligatory, obliging, and obligate.
Some words are:OfficeOfficiencyOffensiveOffenseOf
· itchy
circle
dictionary
octagonoctaneoctaveoctet
There are words that Begin with the prefix tri- like: Triangle, Tripod, Tricycle, and Triceratops
ProcrastinateProtectProfessorProfessProfessionalProactivePro-biotic
phonetic phonethistic
Some words that begin with 'dem' are:demarcationdemeanordemilitarizedemocratdemocracydemocraticdemographicdemonstratedemoralizedemote
chronology, chronograph, chronoscopy, chronometer
democracy,democrat,demodulation,demonstrative
neophite neologism neolithic neotype