US-P18.031ab ।US-P18.031cd ॥
In plain words
Words for fire are used of a firebrand indirectly: what they really refer to is the fire in it. And a face’s reflection is distinct from the actual face, because the reflection follows the mirror.
Close to the Sanskrit
Just as words denoting fire apply to a firebrand and the rest indirectly, since they refer to another thing, so they do not apply there directly. A face’s reflection is different from the face, since it follows the mirror.