These are all words for a unit of language used to express sth.以上各词均为表达意思的语言单位。
word a single unit of language which means sth and can be spoken or written指单词、词、字：◆Do not write more than 200 words.写的东西不要超过 200 字。◆He uses a lot of long words.他使用了很多长词。
term(ratherformal) a word or phrase used as the name of sth, especially one connected with a particular type of language指词语、术语、措辞：◆technical/legal/scientific terms专门/法律/科学用语◆'Old man' is a slang term for 'father'. * old man 为俚语，指父亲。
phrase a group of words which have a particular meaning when used together指短语、词组、惯用法：◆Who coined the phrase 'desktop publishing'?谁创造了 desktop publishing（桌面出版）这个词组？NOTEIn grammar, a phrase is a group of words without a finite verb, especially one that forms part of a sentence: 'the green car' and 'on Friday morning' are phrases.在语法上，phrase 指不含限定动词、构成句子一部分的短语、词组，如 the green car 和 on Friday morning 均为词组。
expression a word or phrase指词语、措辞、表达方式：◆He tends to use a lot of slang expressions that I've never heard before.他往往用许多我以前从未听说过的俚语。
idiom a group of words whose meaning is different from the meanings of the individual words指习语、成语、惯用语：◆'Let the cat out of the bag' is an idiom meaning to tell a secret by mistake. * let the cat out of the bag（让猫从袋子里跑出来）为成语，意为无意中泄露秘密。
Patterns
a word/term for sth
a new word/term/phrase/expression
a technical/colloquial word/term/phrase/expression