Binomials are pairs of words that are commonly joined by and or sometimes or. In English, many of these pairs have a fixed order, so one version sounds natural and the reversed version sounds wrong or unusual.
For example, we usually say bread and butter, black and white, and safe and sound. Most speakers would not normally say butter and bread or sound and safe.
Why is the order fixed? There is not always one simple rule, but several patterns are common:
- Sound and rhythm: one order is simply easier to say, as in back and forth.
- Meaning: the words may follow a natural sequence, as in now and then.
- Usage: people have heard one version so often that it became standard, as in salt and pepper.
Binomials are useful because they make your English sound more natural and fluent. When you learn a common pair, try to memorize it as one unit, not as two separate words. For instance, learn pros and cons together, not just pros and cons separately.
If a word pair sounds slightly strange when reversed, it may be a binomial. Listening for these fixed pairs in reading and conversation is a great way to build natural sounding English.