英 [ˌset ˈfreɪz] 美 [ˌset ˈfreɪz]
固定搭配：一种固定的表达方式，其措辞很少或没有变化，并且可能是习语。
an expression whose meanings cannot be inferred from the meanings of the words that make it up
同义词： idiom / idiomatic expression / phrasal idiom / phrase
成语；固定词组-引用次数：4
参考来源对公文语言中熟语运用的研究
关于“环境”的用法，有一些常用的(frequently-used)固定搭配(set phrase)：学习环境、环境保护、环境污染、环境优美、换换环境、工作环境、生活环境、生态环境等等。
这个之外,另有一种“ 固定词组 ”( set phrase ),即语序与意义皆已固定的习语如:
set phrase 固定词组 ; 固定搭配 ; 固定短语 ; 成语 idiomatic phrase 指常用的固定短语 ; 习语 ; 惯用语 ; 熟语 ..
lose heart是set phrase(固定短语)，意为泄气，加their岂不是画蛇添足？
A set phrase is always fixed.
成语呢是固定格式的。
Notice that this is a set phrase.
注意这是个固定词组。
Can you guess a set phrase with them?
你能猜到一个成语吗？
Obviously other attorneys from around the administration -- lawyers from around the administration were able to express their views, but it is our judgment, the President's judgment, that the action being taken by the United States in its support role for this NATO mission do not meet the threshold set by the War Powers resolution in the hostilities phrase.
And there has been one set of crises which are quite, to use the phrase, exogenous, external to the government which have befallen us.
From the government benches came an answering phrase in the rich bourdon of Geoffrey Cox (Con, Torridge and West Devon), who enthusiastically set about embroidering the same theme with his customary eloquence.