o'clock (adv.)	according to the clock, the exact hour	Let's meet at ten o'clock in the morning.
obey (v.)	to follow orders, to do what you are told to do	When diving you should obey these rules. Otherwise you could be in danger.
object (n.)	something that can be seen or touched	The detective found many things in the room such as a knife and other objects that helped him solve the crime.
obligation (n.)	something a person must do because of law or a promise	We have an obligation to finish this project. We have no other choice
observe (v.)	to watch with interest	You can stand here and observe what is going on below.
occupation (n.)	job, a person's usual work	I'm a doctor. What is your occupation?
ocean (n.)	the large bodies of salty water that cover most of the earth	Baja lies between the Pacific Ocean and the Sea of Cortez.
October	the tenth month	There was a lot of rain in October this year. It is usually rainy in the autumn.
of course	certainly	Of course I know how to make spaghetti! It's very easy. You just boil salted water and put it in.
offer (v.)	to make available	This cafe offers the best cakes and coffee in town. Let's go in.
office (n.)	a room or rooms used as a place of business	You can get information about the tour at our downtown office.
official (adj.)	formal, ceremonial, approved	The official opening of the Festival is next week. The President will be there.
often (adv.)	many times	I often go swimming and diving in the summer, almost every week.
oil (n.)	a greasy liquid from plants or minerals that does not mix with water	The best oil for salads is made from green olives in late summer.
old (adj.)	1. having lived or existed for a long time 2. 7 years old - of a certain age	My great-grandmother is very old. She remembers events that happened before the First World War.
olive (n.)	the fruit of a Mediterranean tree	These olives are green now, but they will turn black later on. They are good for oil and for eating.
one (det.)	a single person or thing	Paris is one of the most interesting cities in the world. Rome is another.
onion (n.)	a vegetable plant which has a bulb with a strong smell and taste	Onions can make you cry, but they add flavour to any dish.
only (adv., adj.)	1. not more than 2. without others	1. It's very close to here, only five stops on the train. 2. Istanbul is the only city in the world on two continents.
open (adj.)	not closed	When is the museum open? I want to see the Persian carpets.
open (v.)	to allow people to enter	The museum opens at 10 o'clock in the morning and closes at 7 o'clock in the evening.
opinion (n.)	a personal belief that is not certain	Everyone has a different opinion about the new film. Some love it and some hate it.
opposite (n.)	person or thing that is different from another	Good is the opposite of bad.
order (v.)	to ask for food in a restaurant	What should we order? I've heard that the seafood in this restaurant is excellent.
ordinary (adj.)	the usual type	This is no ordinary movie. It is very special and took three years to make.
oregano (n.)	dried leaves of a plant used in cooking	Oregano adds an Italian flavour to pasta sauce and salads.
organise (v.)	to arrange according to a system	If we don't organise this office, we'll never find anything! Let's start with these files and letters.
oriental (adj.)	eastern	He loves oriental food. He always eats in Chinese, Thai and Indian restaurants.
original (adj.)	the first known, newly created, not copied	This is an original painting, not a copy.
orphan (n.)	without parents	John is an orphan. His parents are dead.
other (adj.)	different	People tell me carpets are much cheaper in Istanbul than in other cities.
outdoor (adj.)	outside a house or building	I want to visit the outdoor flower market, but I hope it doesn't rain.
outrun (v.)	to run faster than something else	Greyhounds are the fastest dogs on earth. They can even outrun rabbits
outside (adv.)	outdoors, in the open air	Tea helps to cool the body down in summer when it is warm outside.
over (prep.)	onto, above	When the sauce is ready, pour it over cooked spaghetti and mix it in.
overcook (v.)	to cook for too long	Be careful not to overcook the eggs. I like them soft.
owner (n.)	a person to whom something belongs	Where is the owner of this car? It's parked in my space.