| O2 |
symbol of the chemical element oxygen. |
| o |
the fifteenth letter of the English alphabet. |
| oak |
An oak is a kind of tree. It is a strong tree that can grow very big and tall. The wood of an oak is hard, and it is often used to make things like floors and furniture. [2 definitions] |
| oar |
An oar is something that people use to make a boat move or turn in the water. It is a long piece of wood or metal that is wide and flat at one end. An oar is often attached to its boat, but it can move in and out of the water. Boats that use oars usually have two of them. |
| oasis |
An oasis is an area in a desert where there is enough water for plants to grow. The plants are fed by water from a spring or well. |
| oat |
Oats are the seeds of a certain type of grain plant, also called "oats," that grows well in cool climates. Oats are used as food for people and animals. People often eat oats in breakfast cereals, bread, or cookies. |
| oath |
An oath is a very serious promise to tell the truth or to act in a certain way. |
| oatmeal |
Oatmeal is a food substance made by grinding or rolling the seeds of a grain plant called "oats." Rolled oats come out looking like soft, flat flakes. Oatmeal is often cooked and eaten by itself or it is used in making other foods. [2 definitions] |
| obedient |
likely or willing to obey rules or orders. |
| obese |
If someone is obese, they are carrying too much weight on their bodies according to what doctors believe about weight and health. A person who is called "obese" is heavier than a person who is called "overweight." |
| obey |
When you obey someone, you do what that person tells you to do. [2 definitions] |
| obi |
a wide sash worn at the waist over a Japanese kimono. |
| object |
An object is anything that you can see or touch. Objects can be very big or very small. When we talk about objects, we are usually talking about things, not people or animals. [5 definitions] |
| objection |
a statement of not liking or not agreeing with something. [2 definitions] |
| objectionable |
causing someone to object or disagree; offensive. |
| objective |
a goal or purpose that a person works to achieve; aim. [2 definitions] |
| obligate |
to make someone do something because of a law or moral principle. |
| obligation |
An obligation is something that a person must do. If you promise someone that you will do something, then you have a moral obligation to do it. If an adult signs an agreement to do something, then they have a legal obligation to do that thing. Sometimes people feel they have an obligation to do something just because they feel it is the right thing to do. |
| oblige |
to make (someone) feel bound to do something or to act in a certain way. [3 definitions] |
| obliging |
ready to help or do favors. |
| oblique angle |
an angle that is not a right angle. |