See you on Monday x See you Monday

Guys, how should I say:

-See you on monday.

Or

-See you monday.

? .. Thanks

POWER QUESTIONS
O professor das celebridades Daniel Bonatti ensina várias técnicas para você ter conversas melhores mesmo com conhecimentos básicos de inglês. Com as power questions você vai aprender a direcionar a conversa para onde quiser e com isso alcançar seus objetivos na comunicação. ACESSAR AULA
3 respostas
PPAULO 6 49 1.3k
See you on Monday.
See you Monday (in a more colloquial way)
I´ll/we see you Monday. Are you coming or what?

Grammar point:
Perhaps you have already noticed that the days of the week are spelled with the first letter being capital letter, ever.
The same happens when referring to months.
See you on Monday or See you next Monday.
PPAULO 6 49 1.3k
See you on Monday, if colloquially, would assume that is next Monday, or this Monday.
But you are right, and "this Monday" would ring a bit more formal.