opacity, acoustic opacity , 
opal, ,   
opalescent,   
opalesque= opalescent
opaline,  , = opalescent
opaque, , 
opart""
ope. open
open, open sore  ,  {. sore}
open work , , 
openair   , an openair life    
openandshut, 
openarmed  , an openarmed welcome  
opencast  , opencast mining   
openeared 
opener 
openeyed   , 
openfaced  
openfieldopenfield system   ,       
openhanded
openhearted  , , 
opening open, , 
openly, , 
openminded  , , 
openmouthed()   , 
openness, , 
openwork , , 
opera,  
operable, 
operacloak, 
operaglass 
operaglasses 
operahat,  
operahouse 
operand, 
operate, , to operate under a theory    -. 
operated operate, , remotely operated   
operatic, an operatic singer  
operating operate, , operating knife  
operatingroom
operatingtheatre
operation, , 
operational, , operational efficiency 
operative, , 
operatize   -. 
operator, , operator's position  
operetta
ophidian   , , 
ophiolatry
ophite
ophthalmia
ophthalmic
ophthalmologist
ophthalmology
opiate, ,    
opine , 
opinion, , to be of opinion that 
opinionated , , 
opium, 
opium den  
opium joint= opium den
opiumeater 
opodeldoc
opossum,   {. . possum}
oppidan,   ,    
opponent, ,  
opportune, , 
opportunism
opportunist, 
opportunity ,  , to take the opportunity  
oppose,  , 
opposed oppose, , 
opposite,  , 
opposition, , 
oppositionist
oppress, , 
oppression, , 
oppressive, , 
oppressiveness 
oppressor, 
opprobrious, opprobrious language , 
opprobrium, 
oppugn, , 
opt, he opted for the natural sciences    , opt out   
optative, , 
optic, , 
optical, , optical illusion  
optician
optics
optimism
optimist
optimistic, 
optimistical, 
optimum  , , to have an optimum effect   
option,    , I have no option    
optional, 
optophone
opulence, , 
opulent, , 
opus , , opus magnum  
opuscule    
