Liveliness is a spirited or energetic quality. The liveliness of a kindergarten class might be a little overwhelming to a brand-new teacher.
Anyone or anything with liveliness is full of excitement, activity and energy. If you're in search of liveliness on a Friday night, you're more likely to find it at a party or a rock concert than at a sad movie or a solemn poetry reading. We can trace the noun liveliness back to the word life. So if you meet someone who's full of life, its their liveliness that you're noticing.