1. In information theory, the difference between the information content conveyed by the occurrence of an event and the conditional information content conveyed by the occurrence of the same event, given the occurrence of another event; in mathematical notation: x&-{i},y&-{j} is a pair of events, such as an input message x&-{i} and an output message y&-{j}, p(x&-{i},y&-{j}) the joint probability of the occurrence of both events x&-{i} and y&-{j}, p(x&-{i}|y&-{j}) the conditional probability of the occurrence of the event x&-{i}, given the occurrence of the event y&-{j}, p(y&-{j}|x&-{ i}) the conditional probability of the occurrence of the event y&-{j}, given the occurrence of the event x&-{i}, p(x&-{i}) the probability of the occurrence of event x&-{i}, p(y&-{j}) the probability of occurrence of event y&-{j}, then this difference T (x&-{i}|y&-{j}) for the pair of events x&-{i},y&-{j} is expressed as: = T(x&-{i}|y&-{j})=log1p(x&-{i})-log1p(xi|y&-{j}) =logp(x&-{i}|y&-{j})p(x&-{i})=logp(x&-{i},y&-{i})p(x&-{i})p(y&-{j}) =logp(y&-{j}|x&-{i})p(y&-{j})=T(y&-{j}|x&-{i}).

2. 传送信息内容