compass needle
Refers specifically to the magnetic needle of a compass. Often appears in compounds like 羅針盤 (compass).
The compass needle is pointing north.
船乗りは羅針を見て方角を確かめた。
The sailor checked the direction by looking at the compass needle.
Compound of 羅 (gauze, net, or an abbreviation of 羅針盤) and 針 (needle). The exact historical derivation is uncertain, but the spelling is conventionally associated with the compass needle.