| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |
| an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle. |
reaction (rɪˈækʃən) ![]() | |
| —n | |
| 1. | a response to some foregoing action or stimulus |
| 2. | the reciprocal action of two things acting together |
| 3. | opposition to change, esp political change, or a desire to return to a former condition or system |
| 4. | a response indicating a person's feelings or emotional attitude |
| 5. | med |
| a. Compare side effect any effect produced by the action of a drug, esp an adverse effect | |
| b. any effect produced by a substance (allergen) to which a person is allergicthe simultaneous equal and opposite force that acts on a body whenever it exerts a force on another body | |
| 6. | chemical reaction short for nuclear reaction |
| 7. | stock exchange a sharp fall in price interrupting a general rise |
| usage Reaction is used to refer both to an instant response (her reaction was one of amazement) and to a considered response in the form of a statement (the Minister gave his reaction to the court's decision). Some people think this second use is incorrect | |
| re'actional | |
| —adj | |
reaction re·ac·tion (rē-āk'shən)
n.
A response of an organism or living tissue to a stimulus.
The state resulting from such a response.
A chemical change or transformation in which a substance decomposes, combines with other substances, or interchanges constituents with other substances.
The response of cells or tissues to an antigen, as in a test for immunization.
A pattern of behavior constituting a mental disorder or personality type.
reaction (rē-āk'shən) Pronunciation Key
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