Meaning of 合行 in Japanese

彼は１０行に１０個の間違いをした。
He made ten mistakes in as many lines.

もちろん、実際に「はやぶさ」が太陽に近づいているわけではなく、図のように地球から見て太陽の反対側に位置するだけですが、このような現象を「合」と呼びます。
Of course "Hayabusa" is not actually closing in on the Sun, it is just positioned as in the figure so that, seen from the Earth, it is on the opposite side of the Sun; this is called 'conjunction'.