Where does cis come from?
Cis has traditionally been used as a prefix, the same as trans has, and comes from the latin meaning “on the same side as”, which sits opposite trans, from the latin “on the opposite side as”.
These terms have been used in the scientific disciplines for centuries, such as in chemistry, geography, and genetics.
Chemistry has used the terms trans and cis to talk about the arrangement of isomers, which are molecules or ions that have the same formula but different structures. They are used to describe the structure of a molecule, and whether an atom is on the same side as a similar atom, or a different side.
Language is full of these borrowed words, taken from different disciplines or subjects to describe new experiences and understandings of the world. The use of the word cis to talk about gender is just one more way we can make sense of and describe the world around us.
It's also important to use space between cis, trans, and the word they’re attached to, eg. Cis woman and trans woman. You wouldn’t say someone is a smartwoman or a tallwoman.
Why do we need a word for this?
The word cis exists to fill a gap that would otherwise exist in language, and that has previously been filled with words like ‘normal’ or ‘regular’, which position trans people as ‘abnormal’ or ‘irregular’ as a result. While cis people are more common, normal can have a connotation of denigrating trans people. Having a specific word means that our language is not only specific, but value neutral, and doesn’t paint cis or trans people as better or worse as a result.
By being able to differentiate between trans and cis people, we can talk about the experiences we have that differ, and the many more experiences we have that are similar.