Can informal expressions be used in English writing exams? I know spoken expressions and idioms cannot be used, but there are millions of informal words which cannot be recognized immediately in terms of register unless I look them up word by word.

Can informal expressions be used in English writing exams? I know spoken expressions and idioms cannot be used, but there are millions of informal words which cannot be recognized immediately in terms of register unless I look them up word by word.

There are actually three broad registers: (1) formal; (2) informal; (3) neutral (There are other registers as well, but they do not concern us here.)

The vast majority of words in English fall into the “neutal” register. It is important to keep that in mind. It is also important to keep in mind that register is extremely flexible and the boundaries between registers are not rigid. In other words, words, phrases, and expressions that were once in the informal register have shifted into the neutral register and even into the formal register with the passage of time. There are thousands of words and expressions in English that were once considered informal are now routinely used in all situations—formal, informal, and beyond.

Speakers of American English do not generally pay much attention to register, and Americans pride themselves on their “informality”. So, Americans often use informal language in formal situations and think nothing of it. Most Americans are not even aware that there is such a thing as “register” or that there is a difference between formal and informal usage. And because the United States exerts such a powerful influence around the world, American English is gradually changing the face of English as a whole. Even formal British English is now becoming increasingly less formal under the influence of American movies and TV shows.

For example, the expression “from the get-go” used to be considered informal, but you will hear Americans use it in all sorts of formal situations, even in writing business, academic, and professional texts. The neutral equivalent is “from the outset”—however, Americans seem to prefer “from the get-go”.

With regard to the use of idioms, it is not true that you are not supposed to use idioms in English writing exams. Whoever told you that is misinformed. There are thousands of idioms that we use in English that belong in the neutral register and are an essential part of communicating in English at any level of formality. Of course, there are also plenty of idioms that fall into the informal or colloquial register. So, it is a mistake to think that idioms are all automatically “informal” or colloquial.

Here are some idioms that are netural and can be used anywhere and at any level of formality:

sitting on the fence

the tip of the iceberg

a shot in the dark

a lone wolf

strike while the iron is hot

wating in the wings

play second fiddle

and so on

In some of these cases, there is no other way to express the idea, using non-idiomatic language. For example, “the tip of the iceberg” simply cannot be expressed in any other way without having to go into a long an involved explanation.

If I were you, I would not worry about register at all. On your English writing exam, just write as naturally as you can. You are not going to fail the exam if you happened to use a casual expression or two in passing.

With register—as with all other aspects of language—you need to develop a “feel” for it. Memorising the dictionary or stopping to remember which word or phrase is formal and which is informal is not the way to deal with register. You develop a feel for a second language by using it, exposing yourself to it as much as possible, making a few mistakes along the way, and learning from your mistakes.