"The day is hot."
Translation:La tago estas varma.
Depends what you mean by that. If you're trying to say "la tago varma" (without the verb), then it just means "the warm day" and it's not a complete sentence anymore.
On the other hand, with adjectives such as "varma", you can use the derived verbal form (varmi) and conjugate it to the present: "la tago varmas".
- -ega- = modifies the word root, to mean "considerable, major, great" of the root.
eg1: if varma = warm, then varmega = hot
eg2: domo = house, domego = mansion (major-sized house)
-as is roughly equivalent to ending with -a and also using estas in the sentence.
varmeta for lukewarm? (-eta- = tiny, so varmeta = tiny warm)
dometo = cottage (tiny house)