| 1. | An edge is a bridge if it is not contained in a cycle .
一条边是桥当且仅当它不包含在圈中。 |
| 2. | Positive semi-definite matrices are positive definite if and only if they are nonsingular .
正半定矩阵是正定的，当且仅当它们是非奇异矩阵。 |
| 3. | Two sets are said to be equivalent if and only if they can be placed in one-to-one correspondence .
当且仅当两个集合中的元素一一对应时，才称它们为等势。 |
| 4. | Is a unary operator that negates its operand . it is defined for
定义了该运算符，当且仅当操作数为 |
| 5. | A node - set is true if and only if it is non - empty
一个节点当且仅当它不是空节点时，表达式的值为真。 |
| 6. | If and only if exactly one of
对于boolean比较，当且仅当 |
| 7. | A string is true if and only if its length is non - zero
一个字符串当且仅当它的长度不为0是，表达式的值为真。 |
| 8. | Humans can only move robots when told to do so by the referee
当且仅当裁判作出要求时，队员才可移动机器人。 |
| 9. | Humans can only move robots at the instruction of the referee
当且仅当裁判作出要求时，队员才可移动机器人。 |
| 10. | Axiom 1 : if a property is positive , then its negation is not positive
公理1 :一个性质是肯定的当且仅当它的否定是否定的 |
