镇压

Pinyin: zhèn yā
Meaning：Suppression; repression  
Sentence：已派士兵去镇压动乱。Soldiers were sent in to quell the riots..

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镇：

Pinyin: zhèn
Meaning: Small town; to suppress
Radical: 钅
Stokes: 15
Traditional: 鎮
Common words/Phrase:
镇定 [zhèn dìng] 【calm; unperturbed; cool】
镇静 [zhèn jìng] 【calm】
镇痛 [zhèn tòng] 【analgesic】
镇守 [zhèn shǒu] 【guard】

压：

Pinyin: yā,yà
Meaning: To press; to push down
Radical: 厂
Stokes: 6
Traditional: 壓
Common words/Phrase:
压力 [yā lì] 【pressure】
压缩 [yā suō] 【compression】
压抑 [yā yì] 【inhibit】
压制 [yā zhì] 【suppress】
压迫 [yā pò] 【oppress】