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mark (for quick identification or recognition); sign
landmark; guide
「目標」 has another reading with different meanings.
登山者は赤い旗を目標にして山を進んだ。
I proceeded using the red flag as a marker.
遠くに見えるあの建物を目標にしよう。
Let's use that building as a landmark.
地図で目標となる場所をあらかじめ決めた。
I decided on the place to be the marker.