I was two months into my new job in Rio de Janeiro when I asked my co-worker to hand me a hard penis.

His gaze shifted towards me and his eyes paused, narrowed, and a cheeky grin slowly came across his face. Within ten seconds the normally stoic Jose was on the floor, doubled over laughing. “Oh shit,” I thought, “What did I just say?”

It wasn’t the first time I’d made a mistake when learning Portuguese and it wouldn’t be the last. Confusing ‘pão duro’ for ‘pau duro’ (the squiggly line, the tilde, above the ‘a’) proved to be the fatal error – instead of asking for bread, like I had intended, I had asked Jose for something very different.

The nasal tone of the tilde is a critical distinction among many similarly sounding words in Brazilian Portuguese. But no matter how many times I had tried learning the language with audio tapes, YouTube videos, or through immersion, the lesson had never really sunk in until that one fatal error I made with Jose.

I now pay very close attention to the tilde when speaking Portuguese.