This is a frequent question that many English and Spanish speakers have. So, here is a brief explanation that I usually tell my students:
It is an invariable form, which means that there is no gender inflection. Therefore,
-TUDOS pm don’t exist.
TUDO is the antonym of NADA (nothing). You can always substitute one for another. For example:
– Infelizmente, após a enchente, nós perdemos tudo.
– Felizmente, após a enchente, nós não perdemos nada.
These two sentences are completely acceptable. Here is another example:
– Tudo deu certo.
– Nada deu certo.
On the other hand, TODO is a variable form which has gender and number inflections. Thus,
– TODO sm
– TODOS pm
– TODA sf
– TODAS pf are all acceptable!
Usually, these forms come with an article (not necessarily) and a noun before or after:
– Fernando estuda matemática todo dia. (everyday)
However, if I change the placement of todo, the meaning is completely different:
– Fernando estuda matemática o dia todo. (all day long, 24h)
– Ele comeu todas as dez maçãs que comprei. (every single apple)
– Ele comeu a maçã toda. (the entire apple)
Now, let’s compare both of them. In the sentence bellow, I used all of these terms all together:
– Após a enchente, nós perdemos todos os móveis e todas as fotos. Basicamente, a chuva destruiu a casa toda. Nós perdemos tudo.
Here, TUDO summarizes everything mentioned before.
So, the next time you write everybody, you’ll know that the correct form is “TODO mundo”, because todo comes together with a noun.
I hope this topic was usefull for everybody (todo mundo)!