Round or Square?

[Jets]

Ok, so basically I'm running a campaign with my friends and one thing comes to my head every time, is there anything written about the tokens in the map? Is there any rule that specifies the shape of the PCs or NPCs during combat in a battle map? I'm currently using some custom tokens based on WC3 classic icons, but now that I think about it some AOE spells or scenarios would't affect the same as if the NPC has a round shape than if it has a square shape. Any advice?

[Neovirtus]

I believe in 5E a token is considered to be within an AoE if the effect covers more than half the square. The shape of the token doesn't matter.

[Xorn]

In 5E a small/medium creature occupies 1 square, large occupies 2x2, etc. If any square they occupy is 50% or more covered by an AOE that square (and thus creature) is affected. Tokens don't matter, the square(s) they occupy do.

[Jets]

Thank you very much both of you :)