an unstressed vowel
Why is the third letter i rather than e?
Because equus loses its ending and takes an i to join the next word.
an unstressed vowel
Latin does not simply push two nouns together. It trims the first one back to its stem and adds a linking vowel, and for equus that vowel is i. The same joint is visible in a run of English words borrowed whole from Latin compounds, where the i sits in the same place doing the same job. Nothing in the sound marks it, because the syllable it makes is completely unstressed.
The class
An unstressed vowel, flattened until it gives the ear no information.
Same name
Other spellings recorded for equisetum
The name