1. How to form adverbs in all three degrees

2. How to form adverbs from adjectives in all three degrees
Any adjective ending in us-a-um forms its adverb by adding a long ē to the base of the adjective. It doesn’t matter if the adjective is in the positive or superlative degree. If the adj. ends in –us, just change it to long ē.
Examples
Positive Degree Adj. altus-a-um = High/deep
Positive Degree Adv. = altē (long ē) highly, deeply.
Superlative Degree Adj. altissimus-a-um = highest
Superlative Degree Adv. altissimē (long ē) = most highly

3. To form the comparative degree adverb simply…
Use the neuter form of the comparative adj. and there you have it!
e.g.
We know that the adjective altus-a-um in the comparative degree as an adjective is altior, altius. altior is the m/f form and altius is the neuter form. Let’s use “altius,” the neuter adjective form, as an adverb in the comparative degree. How will you tell the difference? How will you know when “altius” is a comparative adjective or if it is a comparative adverb? Easily! If it is an adj., it must agree with a noun, sitting next to it, in gender, number, and case. Look at the next slide!

4. Comparative adjective or adverb….hmmmm.
Puella celerius currit.
Here, celerius is the comparative adverb because it does NOT agree with puella. Puella is feminine and celerius is a neuter form,thereform celeries must be the adverb!
The sentence above means…The girl runs rather quickly.
Try this…Puella celerius quam puer currit.
Here, celerius is still the adverb in the comparative degree. It still doesn’t agree with puella, so this means “The girl runs more quickly than the boy.

5. Now look at these sentences…
Monstrum est altius quam puella.
Here “altius” is the comparative adj. because it agrees with monstrum in gender, number, and case.
The monster is taller than the girl.
or you could write…Monstrum est altius puellā(long ā=abl. sing.).
BUT
Monstrum celerius ambulat.
This could be the rather swift monster walks, since celerius does agree with monstrum in gender, and number, and case.
OR it could be…
The monster walks rather quickly.
You can only tell from context!