By“diction”we mean proper“choice of words”in translation on the basis of accurate comprehension of the original.  English is as complex and sophisticated a Language as Chinese is; and, as is the case with Chinese, a word is capable of being used in five, ten or even more different senses, depending on the different“collocation" or contexts. e. g.
How would you translate“short”in the following sentences? (a) “I have a short memory"，she says. (她说：“我的记忆力不好。”）(b) Liu Hulan's life was short but brilliant. (刘胡兰的一生是短暂而光辉的。）(c) This biscuit eats short.(这饼干吃起来很松脆。) (d) Indeed he has a short temper. (他确实是个急性子。) (e)“Consequently，seeing that they could not win, Lord North in 1778 offered many concessions，short of independence." (“诺斯励爵鉴于不能取胜，于1778年提出要作出若干让步，只是不让他们独立。”）
Then, there is the question of“collocation" in Chinese, e. g.
(a) Electricity lights the streets and buildings, warms the houses, heats food in cookers, works trains and drives the machines in factories making all kinds of products. The Chinese version should preferably read：电照亮街道和建筑物，供家庭取暖，用欢具蒸煮食物，驱动电气 机车，并在工厂里驱动机器加工各种产品。
(b) Supercomputers of the nineties are predicated to support massive parallelism, further reducing computational time and cost. Here,“reduce”has two jectives“time”and“ cost".  In the Chinese version the collocation should be “减少计算时间，降低计算成本”。The whole sentence should read“预计90年代的巨型计算机可保障大规模并行运算，从而可进一步减少计算时间，降低计算成本。”
(c) See Note 10 of Lesson 1, Note 7 of Lesson 22，Note 17 of Lesson 23, etc.
Furthermore，there is the question of making a distinction between“derogatory”terms
(“贬义词”）and "commendatory” terms (“褒义词”）in English-Chinese translation, too, e, g.
He said that once other nations had developed atomic weapons, the world would be like a room full of armed men, each dependent on the good-will of the others to stay alive. In translating this sentence, the sentence adverbial “each (being) dependent on the good -will of the others to stay alive”should preferably be rendered into “每个人都要仰仗其他人的善意才能活命”。