A unit of stellar distance, equal or the distance from the earth to a star with an annual parallax of one second of arc, equivalent to about 3 1/4 light years.

【天】秒差距；视差秒。天文距离单位。天体的日心周年视差为一角秒，它的距离即为一秒差距，相当于三．二六一五光年，或九．四六兆公里。