Singular and Plural Words

In many languages there are certain words which have no singular form, only a plural form. It is called "plurale tantum", which is Latin for "plural only". Very often there no particular reason for it and does not conform to the rules you learn at school.
In English, pluralia tantum, the plural of "plurale tantum" are usually things that function together as pairs or sets: scissors, pants, pajamas, pliers, spectacles, etc.


There is also "singularia tantum", which are words that have no plural form, such as information.

There are some examples of pluralia tantum that have become singularia tantum. One such is 'news', which was originally plural, but is now always singular. 'Data' was originally the plural of 'datum', but is now pretty mostly a singulare tantum.

Some words can be used as ordinary nouns or as plurale tantum, and you can decide which is the most appropriate. For example, if you want to tell somebody they should apply some thought to a matter, you can say either "Use your brain" or "Use your brains". A bad person would want to blow your brains out, rather than just your brain. There are some that we always get two of, such as pants. There is one "pant" on each leg, but we never talk about them separately, because you need both. A pant would signify just one leg hole.