In Rust, the function keyword is written 'fn', there're no assumptions or ambiguity there. You just have to learn "in Rust fn means function". It's as capricious as any other keyword, including function.
As a non-native English speaker I find this amusing because for me it's very clear that keywords are magic incantations for the compiler or interpreter, they aren't meant to explain anything. You just learn how to use those keywords and deal with it. For me, it's not clearer to write function instead of fn because in my native language you write it 'función'.
In my experience, it's not rare for Spanish-speaking programmers to ommit the t in function as it is the clearest and most natural way for them to write it. Then, when the program doesn't work, they have to add the missing ts. I feel fn is an improvement with regards to this, as it's not so English-centered. Let's stop pretending that programming a computer is a mixture of Logic, Math and English.