This is the 562nd most frequent French word.
courant
"Courant" in English means "current" (as in flow, trend, or up-to-date).
Here, 'courant' is used as a noun referring to the flow of water in a river.
Le courant dans la rivière est très fort aujourd'hui.
The current in the river is very strong today.
In this sentence, 'au courant' is an idiomatic expression meaning 'aware' or 'informed' about something.
Elle est au courant des dernières nouvelles.
She is aware of the latest news.
'Courant' is used here as an adjective meaning 'common' or 'frequently encountered'.