I easily get muddled between these two so I sound the words out — breath and breathe. For some reason I decided to pronounce the words wrong and so totally got muddled up. I had the ‘e’ in the middle much longer and the one on the end silent. I figured, English is strange, this is correct. It isn’t. Oh, no. Not one bit.
Breath — the air inhaled / exhaled.
Breathe — inhale / exhale.
You can ‘breathed’ but not ‘breath-ed’.
Now I know! (Until I get muddled again.)