In English the singular is used when modifying another noun like that. For example, a trainer of dogs is a dog trainer, opener of cans is a can opener, a podiatrist a foot doctor, a ball you kick with your feet is a football, etc.
The real question is why does english persist with so many different ways to make plural words
In English the singular is used when modifying another noun like that. For example, a trainer of dogs is a dog trainer, opener of cans is a can opener, a podiatrist a foot doctor, a ball you kick with your feet is a football, etc.
The real question is why does english persist with so many different ways to make plural words
If you have multiple toothbrush you have teethbrush, like lieutenants-general