Dictionary A B C D E F G H I J K L M N O P Q R S T U V W X Y Z identity A number that when an operation is applied to a given number yields that given number. For multiplication, the identity is one and for addition the identity is zero. indefinitely An unspecified amount, having no exact limits (cf Infinity and Iteration Discussion). independent events Two events A and B are independent if the probability that they happen at the same time is the product of the probabilities that each occurs individually; i.e., if P(A & B) = P(A)P(B). In other words, learning that one event occurs does not give any information about whether the other event occurred too: the conditional probability of A given B is the same as the unconditional probability of A, i.e., P(A/B) = P(A). infinity Greater than any fixed counting number, or extending forever. No matter how large a number one thinks of, infinity is larger than it. Infinity has no limits (cf Infinity and Iteration Discussion). initiator A line-segment or figure that begins as the beginning geometric shape for a fractal. The initiator is then replaced by the generator for the fractal. input The number or value that is entered, for example, into a function machine. The number that goes into the machine is the input (cf Functions as Processes or Rules Discussion). integer Any positive or negative number that does not include a fraction or decimal, including zero. intersection of sets The intersection of two or more sets is the set of elements that all the sets have in common; in other words, all the elements contained in every one of the sets. The mathematical symbol for intersection is (cf Internet Search and Set Operations Discussion). intercept See x-intercept or y-intercept (cfLinear Functions Discussion). inverse, additiveA number when added to a given number yields zero. Also see identity. inverse, multiplicativeA number when multiplied by a given number yields one. Also see identity. irregular fractals Complex fractals whose dimension is often difficult to determine and in some cases is unknown (cf Dimension for Irregular Fractals Discussion). isosceles triangle A triangle that has at least two congruent sides (cfTrapezoid Discussion). item The things or objects that are the subject of a bar graph (cf Class Interval: Scale and Impression Discussion). iteration Repeating a set of rules or steps over and over. One step is called an iterate. (cf Infinity and Iteration Discussion). A B C D E F G H I J K L M N O P Q R S T U V W X Y Z