Please tell me the singular form of this word.

In English, adding 's' after a noun makes it a plural form.

After using the computer for a long time, my shoulders became stiff.

He is learning Ancient Greek language.

I learned about the Klein bottle in math class.

Old Church Slavonic is the oldest recorded language of the Slavic group.

Old Church Slavonic is the first language written by the Slavs.

He explained in detail about the structure of the sphenoid bone.

This butterfly valve is used to control the flow of fluid.

The characteristic of annelids is that their bodies are divided into ring-shaped segments.