a doubled consonant
Does equisetum double its s?
No. One s.
a doubled consonant
The stress falls on SEE, and a stressed syllable in English is normally announced by doubling the consonant that follows or precedes it. That is a real pattern and it has been applied here in the right spirit and the wrong language. Latin doubles a consonant only when it genuinely says it twice, and seta has one s.
The class
A consonant doubled to mark a stress, the way English words do it.
Same name
The name