Hi Lukas👋 Brighten up means to make happier or better. For example you could say: "Thank you! You really brightened up my day." meaning you made my day better Lighten up usually means loosen up, stop being grumpy or too serious. For example you could be out with a friend and they look really up tight or worried, you would say something like, "Lighten up won't you." Hope that helps, feel free to contact me if you have any other questions.

Depends really, they can be synonyms, or they can have completely different meanings, it all depends on context, as with everything in the English language. So we have "brighten up" - which can refer to maybe telling someone to be happier or whatever, in that case, it's a synonym for "cheer up", you could say "brighten up the room" as in literally someone turning on the light and brightening up the room (It doesn't always have to have a special meaning, sometimes it can be quite a literal description), you could refer to something literally brightening up, like "The wall really brightened up after painting it" as in it was painted a brighter color than before And then lighten up could also be a synonym for "Cheer up", same as "brighten up", and it's the primary usage of the phrase, like if you ask anyone, that's what they'll say the phrase is used for, so yeah. Now there is an uncommon expression of "lighten up", where someone loses a lot of weight and someone else tells them "You really lightened up, didn't you?" But as I said, that's very uncommon, still, felt like throwing it out there Anyway, i think i rambled enough, hope i explained everything, if you'd like to have a class with me or anything of the sort, you know where to find my profile, see ya

It seems like the answer might depend on the country. For me, brighten up can refer to happiness or intelligence, while lighten up can refer to happiness or burden. I tend toward brighten up on this case.

Brighten: to bring happiness, make happier Lighten: to relieve burden, loosen up, be less strict or less worried