x的y次方，用英语怎么说？

x to the power of y
yth power of x

4 to the power of 7
7th power of 4

Oxford Advanced Learner's English-Chinese Dictionary
Power
[C esp sing 尤作单数] (mathematics 数) result obtained by multiplying a number by itself a certain number of times 乘方; 幂: the third power of 2 (= 2 x 2 x 2 = 8) 2的三次幂（= 2 x 2 x 2 = 8） * the second, third, fourth, etc power of x (= x2, x3, x4, etc) x的二次、 三次、 四次等幂（= x2、 x3、 x4等） * to the power of sth, ie multiplied by itself a certain number of times 某数的自乘 * 44 represents four to the power of four, ie 4 x 4 x 4 x 4 = 256 44表示4自乘4次

x to the yth power

four to the seventh power

4 (four) to the 7th(seventh) power.

一般方法：x的y次方是 x to the yth power.