"Today we are less tired."

Translation: Dziś jesteśmy mniej zmęczone.

[AlonBenach]

Why is zmęczoni a typo? What specified the gender in the given English sentence?

[immery]

it is either zmęczeni or zmęczone.

[JeepBrotha]

How would you say tired because you didn't sleep?

[Jellei]

A sentence like "I am tired because I did not sleep" would be "Jestem [zmęczony/zmęczona], bo nie [spałem/spałam]".

(the first words in brackets are spoken by a man, the second ones by a woman)

EDIT: Alik says that you may be looking for a more concise solution, like a one-word translation :D "niewyspany" is an adjective for someone who didn't sleep well and is tired because of that. "wyspany", on the other hand, is well-rested (due to getting enough sleep).

[JeepBrotha]

Ok thank you, I was looking for a single adjective ;)