平原|へいげんheigen[0]heiban (flat)

1. nounplain; moor; prairie
   初秋しょしゅうの頃ころのほど、その平原へいげんが美うつくしく見みえるときはない。↗

   At no time does the plain look so perfect as in early autumn.

• Synonym平野へいやNeutralRefers to a large expanse of low-lying flat land, as in 「関東平野」; used in both geography and everyday speech, while 「平原」 stresses a vast open field.
• Related広野こうやWrittenA vast open field; written/formal prose, carrying a sense of wide emptiness.
• Antonym山岳さんがくNeutralAntonym: steep, rugged mountains; the opposite of flat 「平原」.
• Antonym山地さんちNeutralAntonym: mountainous terrain; the opposite of plains.

Use 「平原」 for flat, wide open land, as in 「大平原」 or 「平原を駆ける」. For flat land in geographical terms say 「平野」; for a vast, empty field 「広野」. The antonyms are 「山岳」 and 「山地」.

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

1. 平たいらで広ひろい野原のはら。
2. 日本人にほんじんの姓せいのひとつ。