This is a formal occasion.

这是一个正式的场合。

Please set it for a formal occasion.

请上发卷作适合正式场合的发型。

I only wear ties on formal occasion.

我只在正式场合才打领带。

Loosen up, this isn't a formal occasion.

随便一些，这不是正式场合。

Put on your Sunday best. This is a formal occasion.

穿上你最好的礼服。这是个正式场合。