食指|しょくしshokushi[1]atamadaka (head-high)

1. nounindex finger; forefinger

• Synonym人差し指ひとさしゆびNeutralThe everyday, neutral native-Japanese word for the index finger, more common than 食指 in daily speech. It cannot replace 食指 in the idiom 「食指が動く」.
• Synonym示指じしFormalA formal term with a medical and anatomical slant, more specialised than 「食指」; you will mostly meet it in medical writing.

For the finger itself, 「人差し指」 is the everyday choice. 「食指」 is used mostly in the idiom 「食指が動く」, which expresses appetite or interest arising. In medical contexts, use the formal 「示指」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 「人差し指ひとさしゆび」の異称いしょう・漢語かんご表現ひょうげん。
2. （比喩ひゆ　「食指しょくしが動うごく」より）興味きょうみ、嗜好しこう、野心やしん。