This is the 504th most frequent Polish word.
wiadomo
"Wiadomo" means "it is known" or "obviously" in English.
Here, 'wiadomo' is used to mean 'it's known', indicating shared or general knowledge.
Wiadomo, że dziś będzie padać deszcz.
It's known that it will rain today.
In this context, 'wiadomo' conveys 'obviously', indicating an assumed necessity or condition.
Chodźmy na spacer, wiadomo, z parasolem.
Let's go for a walk, obviously with an umbrella.
Here, 'wiadomo' is used colloquially to mean 'of course', asserting agreement with or reinforcement of a statement.