OBEY – (verb) means to do what you are told to do.” A soldier must always obey the instructions of an officer. The bad boy did not obey his father.

OBJECT – (noun) 1. An object is something in the world around us. An object can be almost anything. “A shoe is an object. A pencil is an object. A book is an object. “2. Object also means reason or purpose. It has almost the same meaning as objective. “What is the object of this?” “His object was to get rich.” 3. Object – (verb) has another meaning, but it is spoken differently – ask your teacher. It means to be against something or give a reason why something should not be. For example if y our father says you cannot do something you very much want to you object against his decision and give the reasons why he should let you. A person usually objects against something that he thinks is unfair or something that he really does not like. 4. Then there is the meaning of object in grammar. A verb is a word of doing. The person or thing that does is the subject. The person or thing that has something done to it is called the object. In ‘I see the bird’, ‘I’ is the subject and ‘bird’ is the object. In ‘The car hit the tree’, ‘car’ is the subject and ‘tree’ is the object. In ‘The teacher teaches arithmetic’, ‘teacher’ is the subject and ‘arithmetic’ is the object. See ACTIVE VERB & PASSIVE VERB.

OBJECTIVE – (noun) 1. It means something one is planning to do or get. “His objective in getting good marks at school was to get a good job. Her objective in learning to read was to be able to study nursing. “2. As an adjective it means to be not influenced by one’s own feelings, but only by outward things. “ When making a judgement about one’s children it is difficult to be objective. ” 3. In grammar it is the adjective from the word ‘object’. For example in this sentence ” ” ball’ is” in the objective case.” He hit the ball with his bat. See SUBJECTIVE REALITY.

OBLIGATION – (noun) 1. An obligation is something that you feel you must do. You often say that you are under an obligation to someone else. “I am under an obligation to him to look after his sister because last year he saved my sister from drowning. “ 2. The verb is oblige. “I am obliged to him for saving my sister from drowning.

OBLIQUE – (adjective) means at an angle to some line or surface, but not at right angles or parallel. See diagram 50.

OBLONG – (noun) An oblong is another name for a rectangle. See Diagram 7.

OBSERVATION – (noun) is the action of observing. “Her observation is good. She notices everything.

OBSERVE – (verb) To observe means to see what is around you and to take note of what it is.” An artist should observe things well so he can know the shape and detail of things that he wants to draw. ” “If you do not observe what the teacher is writing on the chalk board you will not be able to do your geometry.

OBTUSE – (adjective) means at an angle which is greater than a right angle, but less than two right angles. See diagram 5.

OBVIOUS – (adjective) is something that is easily seen or understood. “It is obvious that you cannot see anything in a completely dark room. It is obvious that there is something wrong because all the people are running around the streets screaming.

OCCASION – (noun) means a special time. “Her birthday party was a happy occasion. The birth of the king’s first son will be a great occasion.

OCCUPY – (verb) 1. Occupy means to take up some space or a place.” Ten people are occupying this house. You are occupying my chair, please get up. “2. Occupy also means to keep busy with. “ He occupies his spare time by reading many books. He is very interested in motorcars and they occupy his attention all day long.

OCCUR – (verb) means to happen. If you ask when did that occur it is the same as asking when did that happen. “I wonder what will occur tomorrow.

O’CLOCK stands for ‘of the clock’. If you say it is 10 o’clock you just mean that the time is 10 hours. To know exactly what the time is you need to know if it is before noon or after noon – (the hour hand of the clock goes right around the clock two times every day). When it is before noon we use am – (am stands for ante meridiem which in a language called Latin means before midday) So 10 o’clock in the morning is written 10 am and 9 o’clock at night is written 9 pm – (pm stands for post meridiem which means after midday in Latin).

OCTAGON – (noun) An octagon is an 8 sided figure.

ODD – (adjective) An odd number is an integer – (whole number) that cannot be divided by 2 without remainder. 3, 5, 7 are odd numbers. If you divide them by 2 you will get a remainder of 1. See EVEN.

OFFICER – (noun) 1. An officer is the name for a person in the army who is in charge of other soldiers. “The officer gave the order to the soldiers to advance.” See ADVANCE. 2. An officer is also the name for someone on a ship who is charge of other sailors. The captain is the senior officer on a ship. See SENIOR. 

OMIT – (verb) means to leave out. “If you omit the decimal comma you will not get the right answer. If you omit to come she will be very disappointed. 

ONE – (noun) 1. One means a single thing by itself. It is the basic number. One and one make two. 2. One also stands for ‘one person or a person or any person’. If you say, “One should know that”, you mean a person should know that or any person should know that.

OPEN – (adjective) 1. Open means the opposite of shut or closed. See OPPOSITE. “The wind is blowing through the open door.” “Open” – (verb) “the door so I can come in”. 2. In maths one talks about an open figure or an open curve. See diagram 46.

OPERATION – (noun) 1. An operation is something to be done or that was done. “The soldiers carried out the operation against the enemy successfully. “ 2. When doctors do an operation it means that they had to cut into the body and sew it up again. 3. In maths an operation is one of the four operations of addition, subtraction, multiplication or division. See OPERATION SIGN.

OPERATION SIGN – (noun) Plus – (+), minus – (-), multiply – (x) and divide – (<:f240,QLetter Gothic – (Math8),0,0,0>%<:f> &>) are the main operation signs in maths.

OPINION – (noun) Opinion means the ideas that someone has about something. “I asked him what was his opinion of the new teacher. She has a low opinion of Jim because he often tells lies.

OPPOSITE – (preposition) 1. Opposite means face to face. “He sat opposite her on the other side of the table. She lived in the house directly across the road so you can say she lived in the house opposite. ” 2. It also means as different as possible. “ Fast and slow have opposite meanings. Hot and cold also have opposite meanings. They had opposite ideas. She liked staying at home and studying. He liked going out and playing sport. “3. It can also be a noun. You can say for example he and she were opposites. For OPPOSITE ANGLES see diagram 3. For a pair of OPPOSITE SIDES see diagram 7. See diagram 20 for OPPOSITE in relation to trigonometry.

ORDER – (noun) 1. Order means placed in the way you would expect things to be placed without confusion. “Please tidy your rooms and put everything” “into order. 2. “When numbers are placed in order they are placed starting with the smallest and then the next in size and then the next and so on. If you place the numbers 7, 5, 8, 10, 3, 11 in ascending order you would get: 3, 5, 7, 8, 10, 11. If you placed them in descending order you would get: 11, 10, 8, 7, 5, 3. See ASCENDING & DESCENDING. 3. ‘In order to’ means ‘with the purpose of’. “He studied hard in order to pass his exams. In order to be successful you should be hard working”. 4. As a verb ‘to order’ means to tell someone to do something. The officer ordered the soldiers to advance. See OFFICER & ADVANCE.

ORDINAL NUMBER – (noun) An ordinal number is a number which shows order or position. First, second, third and fourth are examples of ordinal numbers. The short way of writing these is 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, 10th and so on. “In what place did he come in class? He came fourth.” See CARDINAL.

ORDINATE – (noun) The ordinate of a point is its distance from the X axis. See diagram 18.

ORIGIN – (noun) 1. Origin means the thing or person from where something comes. “John was the origin of that story; he is the one who started it.” “Trees are the origin of wood. “ 2. In maths the origin is the intersection of the X and Y axis. See Diagram 18.

ORTHOGONAL – (adjective) means at right angles. See RIGHT ANGLE & NORMAL.

ORTHOCENTRE – (noun) See diagram 29.

OVAL – (noun) means two different things in maths. 1. It can mean an ellipse. See Diagram 17. 2. Or it can mean egg-shaped with one end having a smaller radius than the other. 3. Oval is also used to mean a sports field because a lot of sports fields , especially those that can take a large number of spectators, are in the shape of an oval.

OVER – (preposition) 1. Over means on top of or covering. “She put a blanket over the bed. There is a roof over the house. “2. It means from one side across the top to the other side. “ The cat jumped over the wall. “3. It means forward and down. “ The ball rolled over the edge of the table. “4. It means during. “ The road wore badly over a period of years. “5. It means more than. “ He drove at over 150 kilometres per hour. “6. It means having authority. “ The soldiers had a general over them. ” See AUTHORITY. 7. It means through the use of. “I heard that in a talk over the radio.” 8. It means through every part of. “I will go over the information before I decide”. 9. It means on the other side of. “She lives in the house over the river.” 10. It means along. “He drove over the road.” 11. Over and over means again and again. “He asked his father over and over until he said yes.” 12. Over with means finished.” I am over with that book; you can have it now.

OVERDRAFT – (noun) means an overdrawing of an account. See DRAW. This means that there will be a negative balance in the account. The negative balance is called the overdraft. If your bank account becomes overdrawn your bank will ask you to immediately deposit some money to get your balance positive again. However if you have negotiated an overdraft facility bigger than the negative balance everything will be alright, but you will be charged interest on your daily overdraft. See BALANCE, NEGATIVE, POSIT IVE, NEGOTIATE, DEPOSIT, ACCOUNT, OVERDRAFT FACILITY, INTEREST.

OVERDRAFT FACILITY – (noun) This is an arrangement with your bank which allows you to draw more money from your bank account than you have in the account. This results in a negative balance. You pay interest at an agreed amount which is usually the prime overdraft rate plus 1 or 2 per cent. The prime overdraft rate is the rate the bank give to their old and reliable customers.

OVERDRAWN – (adjective) When you have a negative balance in your account the account is said to be overdrawn.

OWE – (verb) 1. Owe means that you must pay money to someone for something. If you buy something on credit, then you owe the person, who sold it to you, the price of what you bought. See CREDIT. 2. You can also owe other things than money. For example if someone saved you from drowning you would owe that person your gratitude – (thankfulness) for saving your life. You can owe loyalty, trust and other things like these.