office A1

/ˈɔ.fɪs/ A room or building where people work, usually at desks.

officer A2

/ˈɒf.ə.sə/ A member of the police.

official A2

/əˈfɪʃəl/ Approved by or coming from a person in authority.

opera B2

/ˈɑp.ə.ɹə/ A dramatic play set to music in which the words are sung rather than spoken.

operate A2

/ˈɑpəɹeɪt/ To control or make a machine, device, or system work.

operator B2

/ˈɑpəˌɹeɪtɚ/ A person who controls a machine or piece of equipment.

operational C1

/ˌɑ.pəˈɹeɪ.ʃə.nəl/ Working and ready to be used.

opulent C2

/ˈɒpjʊlənt/ Showing great wealth and luxury; richly grand.

opulence C2

/ˈɒp.jʊl.əns/ Great wealth shown through luxurious and lavish living.